Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Accumulated other comprehensive income (loss)
Beginning balance	$ 1,574	$ 1,427	$ 1,570	$ 1,399
Other comprehensive income (loss), net of tax	23	(2)	39	(16)
Ending balance	1,656	1,475	1,656	1,475
Investment securities
Accumulated other comprehensive income (loss)
Beginning balance	(31)	(47)	(47)	(18)
Unrealized gain (loss)	22	(12)	43	(44)
Less: Tax provision (benefit)	5	(3)	10	(11)
Net unrealized loss, net of tax	17	(9)	33	(33)
Reclassification out of AOCI	7	0	7	0
Less: Tax provision	1	0	1	0
Net unrealized gain reclassified out of AOCI	6	0	6	0
Reclassification of certain income tax effects	0	0	0	(5)
Other comprehensive income (loss), net of tax	23	(9)	39	(38)
Ending balance	(8)	(56)	(8)	(56)
Cash Flow Hedges
Accumulated other comprehensive income (loss)
Beginning balance	0	17	0	2
Unrealized gain (loss)	0	9	0	28
Less: Tax provision (benefit)	0	2	0	7
Net unrealized loss, net of tax	0	7	0	21
Reclassification out of AOCI	0	0	0	1
Net unrealized gain reclassified out of AOCI	0	0	0	1
Other comprehensive income (loss), net of tax	0	7	0	22
Ending balance	$ 0	$ 24	$ 0	$ 24