Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Accumulated other comprehensive income (loss)
Beginning balance	$ 1,842	$ 1,788	$ 1,574	$ 1,570	$ 1,788	$ 1,570
Amount of loss reclassified from AOCI into income	1				1
Other comprehensive income, net of tax	15	30	23	16	45	39
Ending balance	1,971	1,842	1,656	1,574	1,971	1,656
Investment Securities
Accumulated other comprehensive income (loss)
Beginning balance	35	1	(31)	(47)	1	(47)
Unrealized gain (loss)	27		22		72	43
Less: Tax provision (loss)	6		5		17	10
Net unrealized loss, net of tax	21		17		55	33
Amount of loss reclassified from AOCI into income	0		7		0	7
Less: Tax provision	0		1		0	1
Net unrealized gain reclassified out of AOCI	0		6		0	6
Other comprehensive income, net of tax	21		23		55	39
Ending balance	56	35	(8)	(31)	56	(8)
Cash Flow Hedges
Accumulated other comprehensive income (loss)
Beginning balance	(4)	0	0	0	0	0
Unrealized gain (loss)	(10)		0		(15)	0
Less: Tax provision (loss)	(3)		0		(4)	0
Net unrealized loss, net of tax	(7)		0		(11)	0
Amount of loss reclassified from AOCI into income	1		0		1	0
Other comprehensive income, net of tax	(6)		0		(10)	0
Ending balance	$ (10)	$ (4)	$ 0	$ 0	$ (10)	$ 0