v5.6.4: Critical XBRL Precision Fix

Critical Bug Fix

Issue #564: XBRL Assets values were incorrectly rounded, breaking the balance sheet equation.

Problem

When multiple XBRL facts existed for the same concept/context with different precision (decimals attribute), the code selected the first fact encountered rather than the most precise one.

This caused incorrect values:

• PFE 2017 Assets: $172,000M (wrong) vs $171,797M (correct) — $203M error
• PFE 2018 Assets: $159,000M (wrong) vs $159,422M (correct)
• ZTS 2018 Assets: $10,800M (wrong) vs $10,777M (correct)

Fix

• Added _get_fact_precision() and _select_most_precise_fact() helpers
• Modified fact selection to always prefer higher precision (higher decimals value)
• Added regression tests to prevent future regressions

Impact

Balance sheet equation now balances correctly: Assets = Liabilities + Equity ✓

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Thanks to @mpreiss9 for reporting this issue.