Investment Securities (Investment Table) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Investments [Line Items]
Debt securities, available-for-sale, fair value	$ 30,284	$ 25,303
Debt securities, held-to-maturity, amortized cost	1,568	2,362
Held-to-maturity securities, fair value	1,600	2,307
Debt Securities, held-to-maturity, transfer, amount	943	0	$ 0
Debt Securities, held-to-maturity, transfer, unrealized gain	2
Available-for-sale securities
Schedule of Investments [Line Items]
Debt Securities, held-to-maturity, transfer, amount	945
Securities pledged for Federal Home Loan Bank, at fair value	1,900	9,200
Securities, amount eligible to be repledged or sold by counterparty	118	821
Held-to-maturity securities
Schedule of Investments [Line Items]
Debt Securities, held-to-maturity, transfer, amount	943
Operating Segments \| Insurance operations \| Available-for-sale securities
Schedule of Investments [Line Items]
Deposit securities	12	12
US Treasury \| Available-for-sale securities
Schedule of Investments [Line Items]
Debt securities, available-for-sale, amortized cost	2,059	1,911
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	6	0
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	(17)	(60)
Debt securities, available-for-sale, fair value	2,048	1,851
US States and political subdivisions \| Available-for-sale securities
Schedule of Investments [Line Items]
Debt securities, available-for-sale, amortized cost	623	816
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	19	3
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	(1)	(17)
Debt securities, available-for-sale, fair value	641	802
Foreign government \| Available-for-sale securities
Schedule of Investments [Line Items]
Debt securities, available-for-sale, amortized cost	184	145
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	3	1
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	(1)	(1)
Debt securities, available-for-sale, fair value	186	145
Agency mortgage-backed residential \| Available-for-sale securities
Schedule of Investments [Line Items]
Debt securities, available-for-sale, amortized cost	21,183	17,486
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	257	47
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	(36)	(395)
Debt securities, available-for-sale, fair value	21,404	17,138
Agency mortgage-backed residential \| Held-to-maturity securities
Schedule of Investments [Line Items]
Debt securities, held-to-maturity, amortized cost	1,547	2,319
Debt securities, held-to-maturity, unrecognized gain	38	6
Debt securities, held-to-maturity, unrecognized loss	6	61
Held-to-maturity securities, fair value	1,579	2,264
Mortgage-backed residential \| Available-for-sale securities
Schedule of Investments [Line Items]
Debt securities, available-for-sale, amortized cost	2,841	2,796
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	20	1
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	(11)	(111)
Debt securities, available-for-sale, fair value	2,850	2,686
Agency mortgage-backed commercial \| Available-for-sale securities
Schedule of Investments [Line Items]
Debt securities, available-for-sale, amortized cost	1,344	3
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	44	0
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	(6)	0
Debt securities, available-for-sale, fair value	1,382	3
Mortgage-backed commercial \| Available-for-sale securities
Schedule of Investments [Line Items]
Debt securities, available-for-sale, amortized cost	41	715
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	1	1
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	0	(2)
Debt securities, available-for-sale, fair value	42	714
Asset-backed \| Available-for-sale securities
Schedule of Investments [Line Items]
Debt securities, available-for-sale, amortized cost	365	723
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	3	2
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	0	(2)
Debt securities, available-for-sale, fair value	368	723
Asset-backed \| Held-to-maturity securities
Schedule of Investments [Line Items]
Debt securities, held-to-maturity, amortized cost	21	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	21	43
Corporate debt \| Available-for-sale securities
Schedule of Investments [Line Items]
Debt securities, available-for-sale, amortized cost	1,327	1,286
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	37	1
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	(1)	(46)
Debt securities, available-for-sale, fair value	1,363	1,241
Available-for-sale debt securities \| Available-for-sale securities
Schedule of Investments [Line Items]
Debt securities, available-for-sale, amortized cost	29,967	25,881
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	390	56
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	(73)	(634)
Debt securities, available-for-sale, fair value	30,284	25,303
Held-to-maturity securities
Schedule of Investments [Line Items]
Debt securities, held-to-maturity, amortized cost	1,568	2,362
Debt securities, held-to-maturity, unrecognized gain	38	6
Debt securities, held-to-maturity, unrecognized loss	6	61
Held-to-maturity securities, fair value	1,600	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	$ 915	$ 1,200

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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