Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Accumulated other comprehensive income (loss)
Beginning balance	$ 2,358	$ 2,201	$ 1,842	$ 1,788	$ 2,201	$ 1,788
Other comprehensive income, net of tax	(9)	7	15	30	(2)	45
Ending balance	2,498	2,358	1,971	1,842	2,498	1,971
Investment Securities
Accumulated other comprehensive income (loss)
Beginning balance	37	52	35	1	52	1
Unrealized gain (loss)	(2)		27		(22)	72
Less: Tax provision (benefit)	0		6		(5)	17
Net unrealized gain (loss)	(2)		21		(17)	55
Other comprehensive income, net of tax	(2)		21		(17)	55
Ending balance	35	37	56	35	35	56
Cash Flow Hedges
Accumulated other comprehensive income (loss)
Beginning balance	17	(5)	(4)	0	(5)	0
Unrealized gain (loss)	(9)		(10)		17	(15)
Less: Tax provision (benefit)	(1)		(3)		4	(4)
Net unrealized gain (loss)	(8)		(7)		13	(11)
Reclassifications out of AOCI	1		1		2	1
Less: Tax provision (benefit)	0		0		0	0
Other comprehensive income, net of tax	(7)		(6)		15	(10)
Ending balance	$ 10	$ 17	$ (10)	$ (4)	$ 10	$ (10)