Consolidations and Transfers of Financial Assets Transfers of Financial Assets (Details) (USD $) In Billions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Transfers of Financial Assets [Line Items]
Unpaid principal balance portfolio securitizations	$ 160.4	$ 228.5	$ 225.1
Unconsolidated VIEs [Member]
Transfers of Financial Assets [Line Items]
Principal and interest received on retained interest	1.5	1.7	2.4
Unconsolidated VIEs [Member] | Single Class MBS, REMIC & Megas [Member]
Transfers of Financial Assets [Line Items]
Unpaid principal balance of retained interests	6.3	7.2
Fair value	$ 7.6	$ 8.3