Accumulated Other Comprehensive Income (Loss) (Balances in Accumulated Other Comprehensive Income (Loss) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Total accumulated other comprehensive income	$ (616)	$ (713)
Pre-tax [Member]
Unrecognized net pension and postretirement costs	(947)	(965)
Unrealized net gains (losses) on cash flow hedges	(253)	(254)
Unrealized net gains (losses) on securities available for sale	623	421
FDIC's share of unrealized (gains) losses on securities available for sale under the loss share agreements	(379)	(311)
Other comprehensive income, other, net	(35)	(37)
Total accumulated other comprehensive income	(991)	(1,146)
Deferred tax expense [Member]
Unrecognized net pension and postretirement costs	(355)	(362)
Unrealized net gains (losses) on cash flow hedges	(95)	(95)
Unrealized net gains (losses) on securities available for sale	235	158
FDIC's share of unrealized (gains) losses on securities available for sale under the loss share agreements	(142)	(116)
Other comprehensive income, other, net	(18)	(18)
Total accumulated other comprehensive income	(375)	(433)
Accumulated other comprehensive income (loss) [Member]
Unrecognized net pension and postretirement costs	(592)	(603)
Unrealized net gains (losses) on cash flow hedges	(158)	(159)
Unrealized net gains (losses) on securities available for sale	388	263
FDIC's share of unrealized (gains) losses on securities available for sale under the loss share agreements	(237)	(195)
Other comprehensive income, other, net	(17)	(19)
Total accumulated other comprehensive income	$ (616)	$ (713)