Investment Securities (Investment Table) (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
Jun. 30, 2016	Dec. 31, 2015
Schedule of Investments [Line Items]
Available-for-sale Securities, Amortized Cost Basis	$ 18,017	$ 17,350
Available-for-sale Securities, Gross Unrealized Gains	305	96
Available-for-sale Securities, Gross Unrealized Losses	(125)	(289)
Available-for-sale securities	18,197	17,157
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	571	0
Total agency backed bonds	9,997	7,544
Deposit Assets	15	14
Financial Instruments Owned and Pledged as Collateral, Amount Eligible to be Repledged by Counterparty	492	745
Pledged Assets Separately Reported, Securities Pledged for Federal Home Loan Bank, at Fair Value	492	2,506
Cash Equivalents, at Carrying Value	900	1,000
Held-to-maturity Securities, Fair Value	579	0
Held-to-maturity Securities [Member]
Schedule of Investments [Line Items]
Unrealized Gain on Securities	9	0
Unrealized Gain (Loss) on Investments	(1)	0
Debt Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	17,342	16,542
Available-for-sale Debt Securities Gross Unrealized Gain	299	93
Available-for-sale Debt Securities, Gross Unrealized Loss	(43)	(195)
Available-for-sale Securities, Debt Securities	17,598	16,440
US Treasury and Government [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	265	1,760
Available-for-sale Debt Securities Gross Unrealized Gain	10	0
Available-for-sale Debt Securities, Gross Unrealized Loss	0	(19)
Available-for-sale Securities, Debt Securities	275	1,741
US States and Political Subdivisions Debt Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	701	693
Available-for-sale Debt Securities Gross Unrealized Gain	33	24
Available-for-sale Debt Securities, Gross Unrealized Loss	(1)	(1)
Available-for-sale Securities, Debt Securities	733	716
Foreign Government Debt Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	180	169
Available-for-sale Debt Securities Gross Unrealized Gain	11	8
Available-for-sale Debt Securities, Gross Unrealized Loss	0	0
Available-for-sale Securities, Debt Securities	191	177
Residential Mortgage Backed Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	12,446	10,459
Available-for-sale Debt Securities Gross Unrealized Gain	199	52
Available-for-sale Debt Securities, Gross Unrealized Loss	(28)	(145)
Available-for-sale Securities, Debt Securities	12,617	10,366
Commercial Mortgage Backed Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	513	486
Available-for-sale Debt Securities Gross Unrealized Gain	1	0
Available-for-sale Debt Securities, Gross Unrealized Loss	(8)	(5)
Available-for-sale Securities, Debt Securities	506	481
Asset-backed Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	1,671	1,762
Available-for-sale Debt Securities Gross Unrealized Gain	6	1
Available-for-sale Debt Securities, Gross Unrealized Loss	(3)	(8)
Available-for-sale Securities, Debt Securities	1,674	1,755
Corporate Debt Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	1,566	1,213
Available-for-sale Debt Securities Gross Unrealized Gain	39	8
Available-for-sale Debt Securities, Gross Unrealized Loss	(3)	(17)
Available-for-sale Securities, Debt Securities	1,602	1,204
Equity Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Equity Securities, Amortized Cost Basis	675	808
Available-for-sale Equity Securities, Gross Unrealized Gain	6	3
Available-for-sale Equity Securities, Gross Unrealized Loss	(82)	(94)
Available-for-sale Securities, Equity Securities	$ 599	$ 717

Total agency backed bonds, available for sale.

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