Investment Securities (Investment Table) (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Schedule of Investments [Line Items]
Debt securities, held-to-maturity, amortized cost	$ 2,387	$ 2,362
Held-to-maturity securities, fair value	2,374	2,307
Securities, amount eligible to be repledged or sold by counterparty	985	821
Available-for-sale securities
Schedule of Investments [Line Items]
Securities pledged for Federal Home Loan Bank, at fair value	4,100	9,200
US Treasury \| Available-for-sale securities
Schedule of Investments [Line Items]
Debt securities, available-for-sale, amortized cost	1,990	1,911
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	49	60
Debt securities, available-for-sale, fair value	1,942	1,851
US States and political subdivisions \| Available-for-sale securities
Schedule of Investments [Line Items]
Debt securities, available-for-sale, amortized cost	771	816
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	13	3
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	3	17
Debt securities, available-for-sale, fair value	781	802
Foreign government \| Available-for-sale securities
Schedule of Investments [Line Items]
Debt securities, available-for-sale, amortized cost	170	145
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	2	1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0	1
Debt securities, available-for-sale, fair value	172	145
Agency mortgage-backed residential \| Available-for-sale securities
Schedule of Investments [Line Items]
Debt securities, available-for-sale, amortized cost	18,939	17,486
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	98	47
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	193	395
Debt securities, available-for-sale, fair value	18,844	17,138
Agency mortgage-backed residential \| Held-to-maturity securities
Schedule of Investments [Line Items]
Debt securities, held-to-maturity, amortized cost	2,351	2,319
Debt securities, held-to-maturity, unrecognized gain	15	6
Debt securities, held-to-maturity, unrecognized loss	28	61
Held-to-maturity securities, fair value	2,338	2,264
Agency mortgage-backed commercial \| Available-for-sale securities
Schedule of Investments [Line Items]
Debt securities, available-for-sale, amortized cost	316	3
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	4	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0	0
Debt securities, available-for-sale, fair value	320	3
Mortgage-backed residential \| Available-for-sale securities
Schedule of Investments [Line Items]
Debt securities, available-for-sale, amortized cost	2,912	2,796
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	7	1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	33	111
Debt securities, available-for-sale, fair value	2,886	2,686
Mortgage-backed commercial \| Available-for-sale securities
Schedule of Investments [Line Items]
Debt securities, available-for-sale, amortized cost	725	715
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	2	2
Debt securities, available-for-sale, fair value	723	714
Asset-backed \| Available-for-sale securities
Schedule of Investments [Line Items]
Debt securities, available-for-sale, amortized cost	665	723
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	4	2
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1	2
Debt securities, available-for-sale, fair value	668	723
Asset-backed \| Held-to-maturity securities
Schedule of Investments [Line Items]
Debt securities, held-to-maturity, amortized cost	36	43
Debt securities, held-to-maturity, unrecognized gain	0	0
Debt securities, held-to-maturity, unrecognized loss	0	0
Held-to-maturity securities, fair value	36	43
Corporate debt \| Available-for-sale securities
Schedule of Investments [Line Items]
Debt securities, available-for-sale, amortized cost	1,301	1,286
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	7	1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	14	46
Debt securities, available-for-sale, fair value	1,294	1,241
Available-for-sale debt securities \| Available-for-sale securities
Schedule of Investments [Line Items]
Debt securities, available-for-sale, amortized cost	27,789	25,881
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	136	56
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	295	634
Debt securities, available-for-sale, fair value	27,630	25,303
Held-to-maturity securities
Schedule of Investments [Line Items]
Debt securities, held-to-maturity, amortized cost	2,387	2,362
Debt securities, held-to-maturity, unrecognized gain	15	6
Debt securities, held-to-maturity, unrecognized loss	28	61
Held-to-maturity securities, fair value	2,374	2,307
Federal Home Loan Bank certificates and obligations \| Held-to-maturity securities
Schedule of Investments [Line Items]
Securities pledged for Federal Home Loan Bank, at fair value	1,300	1,200
Insurance operations
Schedule of Investments [Line Items]
Deposit securities	$ 12	$ 12

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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