Investment Securities (Schedule of Available-for-sale Securities Reconciliation) (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
Jun. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	$ 19,265	$ 16,107
Available-for-sale Securities, Gross Unrealized Gains	134	213
Available-for-sale Securities, Gross Unrealized Losses	(257)	(183)
Available-for-sale Securities	19,142	16,137
Total agency backed bonds	8,500	7,557
Deposit Assets	15	15
Financial Instruments Owned and Pledged as Collateral, Amount Eligible to be Repledged by Counterparty	2,170	801
Cash Equivalents, at Carrying Value	1,600	2,000
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	18,225	15,216
Available-for-sale Debt Securities Gross Unrealized Gain	123	164
Available-for-sale Debt Securities, Gross Unrealized Loss	(194)	(149)
Available-for-sale Securities, Debt Securities	18,154	15,231
US Treasury and Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	2,203	1,195
Available-for-sale Debt Securities Gross Unrealized Gain	1	1
Available-for-sale Debt Securities, Gross Unrealized Loss	(29)	(18)
Available-for-sale Securities, Debt Securities	2,175	1,178
US States and Political Subdivisions Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	562	389
Available-for-sale Debt Securities Gross Unrealized Gain	12	17
Available-for-sale Debt Securities, Gross Unrealized Loss	(5)	0
Available-for-sale Securities, Debt Securities	569	406
Foreign Government Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	191	224
Available-for-sale Debt Securities Gross Unrealized Gain	9	8
Available-for-sale Debt Securities, Gross Unrealized Loss	0	0
Available-for-sale Securities, Debt Securities	200	232
Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	11,704	10,431
Available-for-sale Debt Securities Gross Unrealized Gain	85	119
Available-for-sale Debt Securities, Gross Unrealized Loss	(149)	(125)
Available-for-sale Securities, Debt Securities	11,640	10,425
Commercial Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	458	254
Available-for-sale Debt Securities Gross Unrealized Gain	0	0
Available-for-sale Debt Securities, Gross Unrealized Loss	(1)	(1)
Available-for-sale Securities, Debt Securities	457	253
Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	2,053	1,989
Available-for-sale Debt Securities Gross Unrealized Gain	4	5
Available-for-sale Debt Securities, Gross Unrealized Loss	(2)	(3)
Available-for-sale Securities, Debt Securities	2,055	1,991
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	1,054	734
Available-for-sale Debt Securities Gross Unrealized Gain	12	14
Available-for-sale Debt Securities, Gross Unrealized Loss	(8)	(2)
Available-for-sale Securities, Debt Securities	1,058	746
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Equity Securities, Amortized Cost Basis	1,040	891
Available-for-sale Equity Securities, Gross Unrealized Gain	11	49
Available-for-sale Equity Securities, Gross Unrealized Loss	(63)	(34)
Available-for-sale Securities, Equity Securities	$ 988	$ 906

Total agency backed bonds, available for sale.

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