Mortgage Banking Activities, Liability for Mortgage Loan Repurchase Losses (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Liability For Mortgage Loan Repurchase Losses [Abstract]
Balance, beginning of period	$ 586	$ 799	$ 615	$ 899
Provision for repurchase losses:
Loan sales	13	12	23	22
Change in estimate	(31)	(38)	(57)	(42)
Net additions (reductions)	(18)	(26)	(34)	(20)
Losses	(11)	(7)	(24)	(113)
Balance, end of period	$ 557	$ 766	$ 557	$ 766