Investment Securities (Investment Table) (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
Sep. 30, 2016	Dec. 31, 2015
Schedule of Investments [Line Items]
Available-for-sale Securities, Amortized Cost Basis	$ 17,535	$ 17,350
Available-for-sale Securities, Gross Unrealized Gains	268	96
Available-for-sale Securities, Gross Unrealized Losses	(102)	(289)
Available-for-sale securities	17,701	17,157
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	649	0
Held-to-maturity Securities, Fair Value	658	0
Total agency backed bonds	9,772	7,544
Deposit Assets	15	14
Pledged Assets Separately Reported, Securities Pledged for Federal Home Loan Bank, at Fair Value	635	2,506
Financial Instruments Owned and Pledged as Collateral, Amount Eligible to be Repledged by Counterparty	635	745
Cash Equivalents, at Carrying Value	800	1,000
Held-to-maturity Securities [Member]
Schedule of Investments [Line Items]
Unrealized Gain on Securities	10	0
Unrealized Gain (Loss) on Investments	(1)	0
Debt Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	16,904	16,542
Available-for-sale Debt Securities Gross Unrealized Gain	266	93
Available-for-sale Debt Securities, Gross Unrealized Loss	(39)	(195)
Available-for-sale Securities, Debt Securities	17,131	16,440
US Treasury and Government [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	316	1,760
Available-for-sale Debt Securities Gross Unrealized Gain	5	0
Available-for-sale Debt Securities, Gross Unrealized Loss	0	(19)
Available-for-sale Securities, Debt Securities	321	1,741
US States and Political Subdivisions Debt Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	740	693
Available-for-sale Debt Securities Gross Unrealized Gain	26	24
Available-for-sale Debt Securities, Gross Unrealized Loss	(3)	(1)
Available-for-sale Securities, Debt Securities	763	716
Foreign Government Debt Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	170	169
Available-for-sale Debt Securities Gross Unrealized Gain	10	8
Available-for-sale Debt Securities, Gross Unrealized Loss	0	0
Available-for-sale Securities, Debt Securities	180	177
Residential Mortgage Backed Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	11,992	10,459
Available-for-sale Debt Securities Gross Unrealized Gain	180	52
Available-for-sale Debt Securities, Gross Unrealized Loss	(29)	(145)
Available-for-sale Securities, Debt Securities	12,143	10,366
Commercial Mortgage Backed Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	526	486
Available-for-sale Debt Securities Gross Unrealized Gain	1	0
Available-for-sale Debt Securities, Gross Unrealized Loss	(3)	(5)
Available-for-sale Securities, Debt Securities	524	481
Asset-backed Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	1,563	1,762
Available-for-sale Debt Securities Gross Unrealized Gain	8	1
Available-for-sale Debt Securities, Gross Unrealized Loss	(1)	(8)
Available-for-sale Securities, Debt Securities	1,570	1,755
Corporate Debt Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	1,597	1,213
Available-for-sale Debt Securities Gross Unrealized Gain	36	8
Available-for-sale Debt Securities, Gross Unrealized Loss	(3)	(17)
Available-for-sale Securities, Debt Securities	1,630	1,204
Equity Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Equity Securities, Amortized Cost Basis	631	808
Available-for-sale Equity Securities, Gross Unrealized Gain	2	3
Available-for-sale Equity Securities, Gross Unrealized Loss	(63)	(94)
Available-for-sale Securities, Equity Securities	$ 570	$ 717

Total agency backed bonds, available for sale.

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