Investment Securities (Investment Table) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Schedule of Investments [Line Items]
Debt securities, held-to-maturity, amortized cost	$ 2,362	$ 1,899
Held-to-maturity securities, fair value	2,307	1,865
Securities, amount eligible to be repledged or sold by counterparty	821	1,000
US Treasury \| Available-for-sale securities
Schedule of Investments [Line Items]
Debt securities, available-for-sale, amortized cost	1,911	1,831
Debt securities, available-for-sale, unrealized gains	0	0
Debt securities, available-for-sale, unrealized losses	(60)	(54)
Debt securities, available-for-sale, fair value	1,851	1,777
US States and political subdivisions \| Available-for-sale securities
Schedule of Investments [Line Items]
Debt securities, available-for-sale, amortized cost	816	850
Debt securities, available-for-sale, unrealized gains	3	11
Debt securities, available-for-sale, unrealized losses	(17)	(7)
Debt securities, available-for-sale, fair value	802	854
Foreign government \| Available-for-sale securities
Schedule of Investments [Line Items]
Debt securities, available-for-sale, amortized cost	145	153
Debt securities, available-for-sale, unrealized gains	1	2
Debt securities, available-for-sale, unrealized losses	(1)	(1)
Debt securities, available-for-sale, fair value	145	154
Agency mortgage-backed residential \| Available-for-sale securities
Schedule of Investments [Line Items]
Debt securities, available-for-sale, amortized cost	17,486	14,412
Debt securities, available-for-sale, unrealized gains	47	35
Debt securities, available-for-sale, unrealized losses	(395)	(156)
Debt securities, available-for-sale, fair value	17,138	14,291
Agency mortgage-backed residential \| Held-to-maturity securities
Schedule of Investments [Line Items]
Debt securities, held-to-maturity, amortized cost	2,319	1,863
Debt securities, held-to-maturity, unrecognized gain	6	3
Debt securities, held-to-maturity, unrecognized loss	61	37
Held-to-maturity securities, fair value	2,264	1,829
Mortgage-backed residential \| Available-for-sale securities
Schedule of Investments [Line Items]
Debt securities, available-for-sale, amortized cost	2,796	2,517
Debt securities, available-for-sale, unrealized gains	1	11
Debt securities, available-for-sale, unrealized losses	(111)	(34)
Debt securities, available-for-sale, fair value	2,686	2,494
Mortgage-backed commercial \| Available-for-sale securities
Schedule of Investments [Line Items]
Debt securities, available-for-sale, amortized cost	718	541
Debt securities, available-for-sale, unrealized gains	1	1
Debt securities, available-for-sale, unrealized losses	(2)	(1)
Debt securities, available-for-sale, fair value	717	541
Asset-backed \| Available-for-sale securities
Schedule of Investments [Line Items]
Debt securities, available-for-sale, amortized cost	723	933
Debt securities, available-for-sale, unrealized gains	2	4
Debt securities, available-for-sale, unrealized losses	(2)	(1)
Debt securities, available-for-sale, fair value	723	936
Asset-backed \| Held-to-maturity securities
Schedule of Investments [Line Items]
Debt securities, held-to-maturity, amortized cost	43	36
Debt securities, held-to-maturity, unrecognized gain	0	0
Debt securities, held-to-maturity, unrecognized loss	0	0
Held-to-maturity securities, fair value	43	36
Corporate debt \| Available-for-sale securities
Schedule of Investments [Line Items]
Debt securities, available-for-sale, amortized cost	1,286	1,262
Debt securities, available-for-sale, unrealized gains	1	5
Debt securities, available-for-sale, unrealized losses	(46)	(11)
Debt securities, available-for-sale, fair value	1,241	1,256
Available-for-sale debt securities \| Available-for-sale securities
Schedule of Investments [Line Items]
Debt securities, available-for-sale, amortized cost	25,881	22,499
Debt securities, available-for-sale, unrealized gains	56	69
Debt securities, available-for-sale, unrealized losses	(634)	(265)
Debt securities, available-for-sale, fair value	25,303	22,303
Held-to-maturity securities
Schedule of Investments [Line Items]
Debt securities, held-to-maturity, amortized cost	2,362	1,899
Debt securities, held-to-maturity, unrecognized gain	6	3
Debt securities, held-to-maturity, unrecognized loss	61	37
Held-to-maturity securities, fair value	2,307	1,865
Federal Home Loan Bank certificates and obligations \| Available-for-sale securities
Schedule of Investments [Line Items]
Securities pledged for Federal Home Loan Bank, at fair value	9,200	7,800
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	1,200	664
Insurance operations
Schedule of Investments [Line Items]
Deposit securities	$ 12	$ 12

Amortized cost of 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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