Consolidations and Transfers of Financial Assets Transfers of Financial Assets (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Transfers of Financial Assets [Line Items]
Portfolio securitizations: unpaid principal balance	$ 76,100	$ 55,400	$ 188,700	$ 166,300
Unconsolidated VIEs [Member]
Transfers of Financial Assets [Line Items]
Retained interests: principal and interest received	284	$ 273	907	$ 919
Unconsolidated VIEs [Member] | Single Class MBS, REMIC & Megas [Member]
Transfers of Financial Assets [Line Items]
Retained interests: unpaid principal balance	4,500		4,500		$ 5,500
Retained interests: fair value	$ 6,000		$ 6,000		$ 6,800