Variable Interest Entities - Loans Sold to Third-Party Sponsored Securitization Entities (Details) - Variable Interest Entity, Not Primary Beneficiary - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Summary of loan sale activities [Abstract]
Carrying value of loans sold	$ 10,660	$ 12,603	$ 22,799	$ 26,253
Proceeds received from loan sales as cash	48	50	99	89
Proceeds received from loan sales as securities	10,559	12,461	22,588	26,196
Total proceeds received from loan sales	10,607	12,511	22,687	26,285
Gains on loan sales	86	$ 82	177	$ 119
Loans repurchased	11,700		11,700		$ 12,400
Real estate acquired through foreclosure	$ 385		$ 385		$ 464