Accounting for Transfers and Servicing of Financial Assets and Variable Interest Entities (Details Textual) (USD $)	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011
Additional Accounting for Transfers and Servicing of Financial Assets and Variable Interest Entities (Textual) [Abstract]
Unfunded capital commitments related to unconsolidated VIEs	$ 960,000,000		$ 965,000,000
Realized federal and state income tax credits on investments	166,000,000	153,000,000
Amortization expense recorded in tax expense on tax-advantaged investments	89,000,000	58,000,000
Amortization expense recognized in other noninterest expense on tax-advantaged investments	101,000,000	113,000,000
Short-term borrowings related to tender option bond program	5,200,000,000		5,300,000,000
Available-for-sale securities related to the tender option bond program	5,300,000,000		5,400,000,000
Minimum amount of investment in an unconsolidated VIE	1,000,000		1,000,000
Maximum amount of investment in an unconsolidated VIE	37,000,000		37,000,000
Aggregate amount of investments in unconsolidated VIEs	1,900,000,000		1,800,000,000
Company's maximum exposure to unconsolidated VIEs, including any tax implications	5,200,000,000		4,800,000,000
Company's maximum exposure to loss related to community development tax-advantaged investments	1,800,000,000		1,800,000,000
Company's maximum exposure previously recorded tax credits	3,300,000,000		3,000,000,000
Assets related to community development and tax-advantaged investment entities VIEs	5,700,000,000		5,600,000,000
Liabilities related to community development and tax-advantaged investment entities VIEs	4,100,000,000		4,000,000,000
Held-to-maturity Securities [Member]
Accounting for Transfers and Servicing of Financial Assets and Variable Interest Entities (Textual) [Abstract]
Held-to-maturity investment securities related to the conduit, in balance sheet	$ 182,000,000		$ 202,000,000