Investment Securities (Investment Table) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Schedule of Investments [Line Items]
Available-for-sale Securities, Amortized Cost Basis	$ 19,293	$ 17,350
Available-for-sale Securities, Gross Unrealized Gains	68	96
Available-for-sale Securities, Gross Unrealized Losses	(435)	(289)
Available-for-sale securities	18,926	17,157
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	839	0
Held-to-maturity Securities, Fair Value	789	0
Deposit Assets	14	14
Pledged Assets Separately Reported, Securities Pledged for Federal Home Loan Bank, at Fair Value	4,881	2,506
Financial Instruments Owned and Pledged as Collateral, Amount Eligible to be Repledged by Counterparty	737	745
Cash Equivalents, at Carrying Value	300	1,000
Held-to-maturity Securities [Member]
Schedule of Investments [Line Items]
Unrealized Gain on Securities	0	0
Unrealized Gain (Loss) on Investments	(50)	0
Debt Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	18,651	16,542
Available-for-sale Debt Securities Gross Unrealized Gain	61	93
Available-for-sale Debt Securities, Gross Unrealized Loss	(381)	(195)
Available-for-sale Securities, Debt Securities	18,331	16,440
US Treasury and Government [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	1,680	1,760
Available-for-sale Debt Securities Gross Unrealized Gain	0	0
Available-for-sale Debt Securities, Gross Unrealized Loss	(60)	(19)
Available-for-sale Securities, Debt Securities	1,620	1,741
US States and Political Subdivisions Debt Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	794	693
Available-for-sale Debt Securities Gross Unrealized Gain	7	24
Available-for-sale Debt Securities, Gross Unrealized Loss	(19)	(1)
Available-for-sale Securities, Debt Securities	782	716
Foreign Government Debt Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	157	169
Available-for-sale Debt Securities Gross Unrealized Gain	5	8
Available-for-sale Debt Securities, Gross Unrealized Loss	0	0
Available-for-sale Securities, Debt Securities	162	177
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	10,473	7,553
Available-for-sale Debt Securities Gross Unrealized Gain	29	46
Available-for-sale Debt Securities, Gross Unrealized Loss	(212)	(55)
Available-for-sale Securities, Debt Securities	10,290	7,544
Residential Mortgage Backed Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	2,162	2,906
Available-for-sale Debt Securities Gross Unrealized Gain	5	6
Available-for-sale Debt Securities, Gross Unrealized Loss	(70)	(90)
Available-for-sale Securities, Debt Securities	2,097	2,822
Commercial Mortgage Backed Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	537	486
Available-for-sale Debt Securities Gross Unrealized Gain	2	0
Available-for-sale Debt Securities, Gross Unrealized Loss	(2)	(5)
Available-for-sale Securities, Debt Securities	537	481
Asset-backed Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	1,396	1,762
Available-for-sale Debt Securities Gross Unrealized Gain	6	1
Available-for-sale Debt Securities, Gross Unrealized Loss	(2)	(8)
Available-for-sale Securities, Debt Securities	1,400	1,755
Corporate Debt Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	1,452	1,213
Available-for-sale Debt Securities Gross Unrealized Gain	7	8
Available-for-sale Debt Securities, Gross Unrealized Loss	(16)	(17)
Available-for-sale Securities, Debt Securities	1,443	1,204
Equity Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Equity Securities, Amortized Cost Basis	642	808
Available-for-sale Equity Securities, Gross Unrealized Gain	7	3
Available-for-sale Equity Securities, Gross Unrealized Loss	(54)	(94)
Available-for-sale Securities, Equity Securities	595	$ 717
Federal Home Loan Bank Certificates and Obligations (FHLB) [Member]
Schedule of Investments [Line Items]
Held-to-maturity Securities, Fair Value	$ 87