Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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+ Details

Fair Value Measurement and Fair Value of Financial Instruments - Significant Unobservable Inputs Level 3 Assets and Liabilities (Detail) (USD $) In Millions, unless otherwise specified			6 Months Ended
	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2013 Minimum [Member] Return on equity [Member]	Jun. 30, 2013 Minimum [Member] Discounted cash flow [Member]	Jun. 30, 2013 Maximum [Member] Return on equity [Member]	Jun. 30, 2013 Maximum [Member] Discounted cash flow [Member]	Jun. 30, 2013 Weighted Average [Member] Return on equity [Member]	Jun. 30, 2013 Weighted Average [Member] Discounted cash flow [Member]	Jun. 30, 2013 Level 3 [Member] Direct bank purchase bonds [Member]	Jun. 30, 2013 Level 3 [Member] FDIC clawback liability [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Market-required return on capital			8.00%		10.00%		10.00%
Probability of default			0.00%	0.10%	8.00%	100.00%	0.60%	55.50%
Loss severity			10.00%	20.00%	75.00%	100.00%	34.70%	43.30%
Securities available for sale	$ 23,510	$ 21,352							$ 1,703
Other liabilities	$ 1,866	$ 2,102								$ 90