Mortgage Banking Activities, Amortized Mortgage Servicing Rights (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Changes in amortized MSRs
Amortization	$ (58)	$ (66)	$ (172)	$ (193)
Valuation Allowance
Reversal of provision (provision) for mortgage servicing rights in excess of fair value	0	(30)	0	(37)
Amortized mortgage servicing rights, net	1,144		1,144		1,408
Amortized [Member]
Changes in amortized MSRs
Balance, beginning of period	1,130	1,432	1,445	1,422
Purchases	42	21	134	102
Servicing from securitizations or asset transfers	30	50	(263)	106
Amortization	(58)	(66)	(172)	(193)
Balance, end of period	1,144	1,437	1,144	1,437
Valuation Allowance
Balance, beginning of period	0	(10)	(37)	(3)
Reversal of provision (provision) for mortgage servicing rights in excess of fair value	0	(30)	37	(37)
Balance, end of period	0	(40)	0	(40)
Amortized mortgage servicing rights, net	1,144	1,397	1,144	1,397
Fair value of amortized MSRs:
Beginning of period	1,450	1,805	1,756	1,812
End of period	$ 1,399	$ 1,759	$ 1,399	$ 1,759