Amortized Cost, Gross Unrealized Gains and Losses and Fair Value of Securities (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Gain (Loss) on Investments [Line Items]
Fair value	$ 93,409	$ 82,007
Available-for-sale
Gain (Loss) on Investments [Line Items]
Fair value	84,540	78,467
Government Sponsored and Guaranteed Entities, and Sovereign Debt Securities | Available-for-sale
Gain (Loss) on Investments [Line Items]
Fair value	$ 9,000	$ 13,100