Loans and Leases (Carrying Value of Purchased Impaired and Nonimpaired Loans) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Residential mortgage	$ 20,581	$ 17,550
Total covered	4,867	6,194
Other acquired	39	58
Purchased Impaired Loans [Member]
Residential mortgage	647	733
Commercial real estate	1,407	2,031
Commercial	68	91
Total covered	2,122	2,855
Other acquired	2	3
Total	2,124	2,858
Allowance for loan losses	(113)	(90)
Net	2,011	2,768
Purchased Nonimpaired Loans [Member]
Residential mortgage	617	713
Commercial real estate	1,597	1,982
Commercial	531	644
Total covered	2,745	3,339
Other acquired	37	55
Total	2,782	3,394
Allowance for loan losses	(36)	(54)
Net	2,746	3,340
Purchased Impaired and Nonimpaired Loans [Member]
Residential mortgage	1,264	1,446
Commercial real estate	3,004	4,013
Commercial	599	735
Total covered	4,867	6,194
Other acquired	39	58
Total	4,906	6,252
Allowance for loan losses	(149)	(144)
Net	$ 4,757	$ 6,108