Loans - Modified in TDRs (Details 4) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011	Dec. 31, 2010
Other Consumer [Member]
Financing Receivable, Modifications [Line Items]
Loans modified in troubled debt restructurings	$ 469	$ 503
TDRs on nonaccrual status	262	291
Consumer Loans Auto Financing Receivable [Member]
Financing Receivable, Modifications [Line Items]
Loans modified in troubled debt restructurings	91	88
TDRs on nonaccrual status	41	38
Consumer business banking
Financing Receivable, Modifications [Line Items]
Loans modified in troubled debt restructurings	378	415
TDRs on nonaccrual status	221	253
Wholesale
Financing Receivable, Modifications [Line Items]
Loans modified in troubled debt restructurings	664	750	449	1,143
TDRs on nonaccrual status	525	578
Additional commitments to lend to borrowers whose loans have been modified in TDRs	15	147
Wholesale | Commercial and industrial [Member]
Financing Receivable, Modifications [Line Items]
Loans modified in troubled debt restructurings	419	531
TDRs on nonaccrual status	314	415
Additional commitments to lend to borrowers whose loans have been modified in TDRs	15	147
Wholesale | Real estate [Member]
Financing Receivable, Modifications [Line Items]
Loans modified in troubled debt restructurings	148	176
TDRs on nonaccrual status	116	128
Additional commitments to lend to borrowers whose loans have been modified in TDRs	0	0
Wholesale | Financial institutions [Member]
Financing Receivable, Modifications [Line Items]
Loans modified in troubled debt restructurings	0	2
TDRs on nonaccrual status	0	0
Additional commitments to lend to borrowers whose loans have been modified in TDRs	0	0
Wholesale | Government agencies [Member]
Financing Receivable, Modifications [Line Items]
Loans modified in troubled debt restructurings	13	16
TDRs on nonaccrual status	13	16
Additional commitments to lend to borrowers whose loans have been modified in TDRs	0	0
Wholesale | Other [Member]
Financing Receivable, Modifications [Line Items]
Loans modified in troubled debt restructurings	84	25
TDRs on nonaccrual status	82	19
Additional commitments to lend to borrowers whose loans have been modified in TDRs	$ 0	$ 0