diff --git a/haddock-api/src/Haddock/Backends/Xhtml/Layout.hs b/haddock-api/src/Haddock/Backends/Xhtml/Layout.hs
index 25d8b07a30..f171f8ddb3 100644
--- a/haddock-api/src/Haddock/Backends/Xhtml/Layout.hs
+++ b/haddock-api/src/Haddock/Backends/Xhtml/Layout.hs
@@ -203,7 +203,7 @@ subInstances :: Maybe Package -> Qualification
              -> [(SubDecl, Maybe Module, Located DocName)] -> Html
 subInstances pkg qual nm lnks splice = maybe noHtml wrap . instTable
   where
-    wrap contents = subSection (hdr +++ collapseDetails id_ DetailsOpen (summary +++ contents))
+    wrap contents = subSection (hdr +++ collapseDetails id_ DetailsClosed (summary +++ contents))
     instTable = subTableSrc pkg qual lnks splice
     subSection = thediv ! [theclass "subs instances"]
     hdr = h4 ! collapseControl id_ "instances" << "Instances"
diff --git a/html-test/ref/Bug26.html b/html-test/ref/Bug26.html
index 2a316f2dfe..36de60b8dc 100644
--- a/html-test/ref/Bug26.html
+++ b/html-test/ref/Bug26.html
@@ -153,7 +153,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:C"
 	    >Instances</h4
-	    ><details id="i:C" open="open"
+	    ><details id="i:C"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table
diff --git a/html-test/ref/Bug294.html b/html-test/ref/Bug294.html
index d0f5f8f368..a71faac3a6 100644
--- a/html-test/ref/Bug294.html
+++ b/html-test/ref/Bug294.html
@@ -57,7 +57,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:A"
 	    >Instances</h4
-	    ><details id="i:A" open="open"
+	    ><details id="i:A"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table
@@ -197,7 +197,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:TP"
 	    >Instances</h4
-	    ><details id="i:TP" open="open"
+	    ><details id="i:TP"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table
@@ -259,7 +259,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:DP"
 	    >Instances</h4
-	    ><details id="i:DP" open="open"
+	    ><details id="i:DP"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table
@@ -321,7 +321,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:TO-39-"
 	    >Instances</h4
-	    ><details id="i:TO-39-" open="open"
+	    ><details id="i:TO-39-"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table
diff --git a/html-test/ref/Bug548.html b/html-test/ref/Bug548.html
index c8c30c231b..a67da9dc0a 100644
--- a/html-test/ref/Bug548.html
+++ b/html-test/ref/Bug548.html
@@ -95,7 +95,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:WrappedArrow"
 	    >Instances</h4
-	    ><details id="i:WrappedArrow" open="open"
+	    ><details id="i:WrappedArrow"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table
diff --git a/html-test/ref/Bug613.html b/html-test/ref/Bug613.html
index 883ae9a54e..4fae0be172 100644
--- a/html-test/ref/Bug613.html
+++ b/html-test/ref/Bug613.html
@@ -99,7 +99,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:Functor"
 	    >Instances</h4
-	    ><details id="i:Functor" open="open"
+	    ><details id="i:Functor"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table
@@ -221,7 +221,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:ThreeVars"
 	    >Instances</h4
-	    ><details id="i:ThreeVars" open="open"
+	    ><details id="i:ThreeVars"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table
diff --git a/html-test/ref/Bug679.html b/html-test/ref/Bug679.html
index 52fc80e4e5..e8527a4660 100644
--- a/html-test/ref/Bug679.html
+++ b/html-test/ref/Bug679.html
@@ -71,7 +71,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:Bar"
 	    >Instances</h4
-	    ><details id="i:Bar" open="open"
+	    ><details id="i:Bar"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table
@@ -145,7 +145,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:Foo"
 	    >Instances</h4
-	    ><details id="i:Foo" open="open"
+	    ><details id="i:Foo"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table
diff --git a/html-test/ref/Bug7.html b/html-test/ref/Bug7.html
index 1ed51b3ecb..bbe0bd612d 100644
--- a/html-test/ref/Bug7.html
+++ b/html-test/ref/Bug7.html
@@ -106,7 +106,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:Foo"
 	    >Instances</h4
-	    ><details id="i:Foo" open="open"
+	    ><details id="i:Foo"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table
@@ -162,7 +162,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:Bar"
 	    >Instances</h4
-	    ><details id="i:Bar" open="open"
+	    ><details id="i:Bar"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table
diff --git a/html-test/ref/Hash.html b/html-test/ref/Hash.html
index 438375f00e..a4cdf87bd4 100644
--- a/html-test/ref/Hash.html
+++ b/html-test/ref/Hash.html
@@ -296,7 +296,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:Hash"
 	    >Instances</h4
-	    ><details id="i:Hash" open="open"
+	    ><details id="i:Hash"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table
diff --git a/html-test/ref/HiddenInstances.html b/html-test/ref/HiddenInstances.html
index c580984543..2fdcf0c07a 100644
--- a/html-test/ref/HiddenInstances.html
+++ b/html-test/ref/HiddenInstances.html
@@ -81,7 +81,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:VisibleClass"
 	    >Instances</h4
-	    ><details id="i:VisibleClass" open="open"
+	    ><details id="i:VisibleClass"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table
@@ -165,7 +165,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:VisibleData"
 	    >Instances</h4
-	    ><details id="i:VisibleData" open="open"
+	    ><details id="i:VisibleData"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table
diff --git a/html-test/ref/HiddenInstancesB.html b/html-test/ref/HiddenInstancesB.html
index cb42dcbf1d..e681f93cbe 100644
--- a/html-test/ref/HiddenInstancesB.html
+++ b/html-test/ref/HiddenInstancesB.html
@@ -81,7 +81,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:Foo"
 	    >Instances</h4
-	    ><details id="i:Foo" open="open"
+	    ><details id="i:Foo"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table
@@ -135,7 +135,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:Bar"
 	    >Instances</h4
-	    ><details id="i:Bar" open="open"
+	    ><details id="i:Bar"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table
diff --git a/html-test/ref/Instances.html b/html-test/ref/Instances.html
index 308b97ce6b..4309c9ae87 100644
--- a/html-test/ref/Instances.html
+++ b/html-test/ref/Instances.html
@@ -71,7 +71,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:-60--126--126-"
 	    >Instances</h4
-	    ><details id="i:-60--126--126-" open="open"
+	    ><details id="i:-60--126--126-"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table
@@ -183,7 +183,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:Foo"
 	    >Instances</h4
-	    ><details id="i:Foo" open="open"
+	    ><details id="i:Foo"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table
@@ -695,7 +695,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:Bar"
 	    >Instances</h4
-	    ><details id="i:Bar" open="open"
+	    ><details id="i:Bar"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table
@@ -1263,7 +1263,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:Baz"
 	    >Instances</h4
-	    ><details id="i:Baz" open="open"
+	    ><details id="i:Baz"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table
@@ -1637,7 +1637,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:Quux"
 	    >Instances</h4
-	    ><details id="i:Quux" open="open"
+	    ><details id="i:Quux"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table
@@ -1995,7 +1995,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:Norf"
 	    >Instances</h4
-	    ><details id="i:Norf" open="open"
+	    ><details id="i:Norf"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table
diff --git a/html-test/ref/OrphanInstancesClass.html b/html-test/ref/OrphanInstancesClass.html
index 4ddfc4b282..e6e46b82b6 100644
--- a/html-test/ref/OrphanInstancesClass.html
+++ b/html-test/ref/OrphanInstancesClass.html
@@ -71,7 +71,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:AClass"
 	    >Instances</h4
-	    ><details id="i:AClass" open="open"
+	    ><details id="i:AClass"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table
diff --git a/html-test/ref/OrphanInstancesType.html b/html-test/ref/OrphanInstancesType.html
index 02aae12dcb..9a55a07bf9 100644
--- a/html-test/ref/OrphanInstancesType.html
+++ b/html-test/ref/OrphanInstancesType.html
@@ -73,7 +73,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:AType"
 	    >Instances</h4
-	    ><details id="i:AType" open="open"
+	    ><details id="i:AType"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table
diff --git a/html-test/ref/QuasiExpr.html b/html-test/ref/QuasiExpr.html
index cbec974294..f87b714250 100644
--- a/html-test/ref/QuasiExpr.html
+++ b/html-test/ref/QuasiExpr.html
@@ -107,7 +107,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:Expr"
 	    >Instances</h4
-	    ><details id="i:Expr" open="open"
+	    ><details id="i:Expr"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table
@@ -229,7 +229,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:BinOp"
 	    >Instances</h4
-	    ><details id="i:BinOp" open="open"
+	    ><details id="i:BinOp"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table
diff --git a/html-test/ref/SpuriousSuperclassConstraints.html b/html-test/ref/SpuriousSuperclassConstraints.html
index 80b0079561..f0c53ca50a 100644
--- a/html-test/ref/SpuriousSuperclassConstraints.html
+++ b/html-test/ref/SpuriousSuperclassConstraints.html
@@ -83,7 +83,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:SomeType"
 	    >Instances</h4
-	    ><details id="i:SomeType" open="open"
+	    ><details id="i:SomeType"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table
diff --git a/html-test/ref/Test.html b/html-test/ref/Test.html
index b8d7f2511a..3dedf5c943 100644
--- a/html-test/ref/Test.html
+++ b/html-test/ref/Test.html
@@ -1659,7 +1659,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:D"
 	    >Instances</h4
-	    ><details id="i:D" open="open"
+	    ><details id="i:D"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table
diff --git a/html-test/ref/TypeFamilies.html b/html-test/ref/TypeFamilies.html
index f857df2a50..2e3b3ccbfa 100644
--- a/html-test/ref/TypeFamilies.html
+++ b/html-test/ref/TypeFamilies.html
@@ -215,7 +215,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:X"
 	    >Instances</h4
-	    ><details id="i:X" open="open"
+	    ><details id="i:X"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table
@@ -679,7 +679,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:Y"
 	    >Instances</h4
-	    ><details id="i:Y" open="open"
+	    ><details id="i:Y"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table
@@ -1061,7 +1061,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:Z"
 	    >Instances</h4
-	    ><details id="i:Z" open="open"
+	    ><details id="i:Z"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table
@@ -1155,7 +1155,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:Test"
 	    >Instances</h4
-	    ><details id="i:Test" open="open"
+	    ><details id="i:Test"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table
@@ -1239,7 +1239,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:Foo"
 	    >Instances</h4
-	    ><details id="i:Foo" open="open"
+	    ><details id="i:Foo"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table
@@ -1347,7 +1347,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:Bat"
 	    >Instances</h4
-	    ><details id="i:Bat" open="open"
+	    ><details id="i:Bat"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table
@@ -1579,7 +1579,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:Assoc"
 	    >Instances</h4
-	    ><details id="i:Assoc" open="open"
+	    ><details id="i:Assoc"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table
@@ -1759,7 +1759,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:-60--62-"
 	    >Instances</h4
-	    ><details id="i:-60--62-" open="open"
+	    ><details id="i:-60--62-"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table
@@ -1909,7 +1909,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:-62--60-"
 	    >Instances</h4
-	    ><details id="i:-62--60-" open="open"
+	    ><details id="i:-62--60-"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table
diff --git a/html-test/ref/TypeFamilies2.html b/html-test/ref/TypeFamilies2.html
index b4d1faa684..61e74333d7 100644
--- a/html-test/ref/TypeFamilies2.html
+++ b/html-test/ref/TypeFamilies2.html
@@ -87,7 +87,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:W"
 	    >Instances</h4
-	    ><details id="i:W" open="open"
+	    ><details id="i:W"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table
@@ -193,7 +193,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:Foo"
 	    >Instances</h4
-	    ><details id="i:Foo" open="open"
+	    ><details id="i:Foo"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table
@@ -299,7 +299,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:Bar"
 	    >Instances</h4
-	    ><details id="i:Bar" open="open"
+	    ><details id="i:Bar"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table
diff --git a/html-test/ref/TypeFamilies3.html b/html-test/ref/TypeFamilies3.html
index eb1644fd20..a87acf63af 100644
--- a/html-test/ref/TypeFamilies3.html
+++ b/html-test/ref/TypeFamilies3.html
@@ -129,7 +129,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:Bar"
 	    >Instances</h4
-	    ><details id="i:Bar" open="open"
+	    ><details id="i:Bar"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table
@@ -227,7 +227,7 @@
 	  ><div class="subs instances"
 	  ><h4 class="instances details-toggle-control details-toggle" data-details-id="i:Baz"
 	    >Instances</h4
-	    ><details id="i:Baz" open="open"
+	    ><details id="i:Baz"
 	    ><summary class="hide-when-js-enabled"
 	      >Instances details</summary
 	      ><table