Investment Securities (Schedule of Available-for-sale Securities Reconciliation) (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
Sep. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	$ 18,782	$ 16,107
Available-for-sale Securities, Gross Unrealized Gains	180	213
Available-for-sale Securities, Gross Unrealized Losses	(204)	(183)
Available-for-sale Securities	18,758	16,137
Total agency backed bonds	8,536	7,557
Deposit Assets	15	15
Financial Instruments Owned and Pledged as Collateral, Amount Eligible to be Repledged by Counterparty	1,702	801
Cash Equivalents, at Carrying Value	1,300	2,000
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	17,685	15,216
Available-for-sale Debt Securities Gross Unrealized Gain	179	164
Available-for-sale Debt Securities, Gross Unrealized Loss	(91)	(149)
Available-for-sale Securities, Debt Securities	17,773	15,231
US Treasury and Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	1,805	1,195
Available-for-sale Debt Securities Gross Unrealized Gain	5	1
Available-for-sale Debt Securities, Gross Unrealized Loss	(1)	(18)
Available-for-sale Securities, Debt Securities	1,809	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	635	389
Available-for-sale Debt Securities Gross Unrealized Gain	17	17
Available-for-sale Debt Securities, Gross Unrealized Loss	(1)	0
Available-for-sale Securities, Debt Securities	651	406
Foreign Government Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	176	224
Available-for-sale Debt Securities Gross Unrealized Gain	8	8
Available-for-sale Debt Securities, Gross Unrealized Loss	0	0
Available-for-sale Securities, Debt Securities	184	232
Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	11,560	10,431
Available-for-sale Debt Securities Gross Unrealized Gain	130	119
Available-for-sale Debt Securities, Gross Unrealized Loss	(76)	(125)
Available-for-sale Securities, Debt Securities	11,614	10,425
Commercial Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	519	254
Available-for-sale Debt Securities Gross Unrealized Gain	0	0
Available-for-sale Debt Securities, Gross Unrealized Loss	(2)	(1)
Available-for-sale Securities, Debt Securities	517	253
Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	1,947	1,989
Available-for-sale Debt Securities Gross Unrealized Gain	6	5
Available-for-sale Debt Securities, Gross Unrealized Loss	(2)	(3)
Available-for-sale Securities, Debt Securities	1,951	1,991
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	1,043	734
Available-for-sale Debt Securities Gross Unrealized Gain	13	14
Available-for-sale Debt Securities, Gross Unrealized Loss	(9)	(2)
Available-for-sale Securities, Debt Securities	1,047	746
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Equity Securities, Amortized Cost Basis	1,097	891
Available-for-sale Equity Securities, Gross Unrealized Gain	1	49
Available-for-sale Equity Securities, Gross Unrealized Loss	(113)	(34)
Available-for-sale Securities, Equity Securities	$ 985	$ 906

Total agency backed bonds, available for sale.

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