Goodwill and Other Intangible Assets - Key Economic Assumptions (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Weighted-average prepayment speed assumption (“CPR”)	9.81%	9.80%
Impact on fair value of 10% adverse change	$ (275)	$ (337)
Impact on fair value of 20% adverse change	$ (529)	$ (652)
Weighted-average option adjusted spread	9.02%	9.43%
Impact on fair value of 100 basis points adverse change	$ (258)	$ (300)
Impact on fair value of 200 basis points adverse change	$ (498)	$ (578)