Loans and Leases (Carrying Value of Purchased Impaired and Nonimpaired Loans) (Details) (USD $) In Millions	Sep. 30, 2011	Dec. 31, 2010
Residential mortgage	$ 19,361	$ 17,550
Total covered	5,222	6,194
Other acquired	47	58
Purchased Impaired Loans [Member]
Residential mortgage	676	733
Commercial real estate	1,587	2,031
Commercial	62	91
Total covered	2,325	2,855
Other acquired	2	3
Total	2,327	2,858
Allowance for loan losses	(64)	(90)
Net	2,263	2,768
Purchased Nonimpaired Loans [Member]
Residential mortgage	646	713
Commercial real estate	1,742	1,982
Commercial	509	644
Total covered	2,897	3,339
Other acquired	45	55
Total	2,942	3,394
Allowance for loan losses	(49)	(54)
Net	2,893	3,340
Purchased Impaired and Nonimpaired Loans [Member]
Residential mortgage	1,322	1,446
Commercial real estate	3,329	4,013
Commercial	571	735
Total covered	5,222	6,194
Other acquired	47	58
Total	5,269	6,252
Allowance for loan losses	(113)	(144)
Net	$ 5,156	$ 6,108