Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Accumulated other comprehensive income (loss)
Beginning balance	$ 1,529	$ 1,373
Ending balance	1,286	1,504
Accumulated Other Comprehensive Income (Loss)
Accumulated other comprehensive income (loss)
Beginning balance	2	8
Net unrealized loss, net of tax	(27)	4
Reclassifications out of AOCI	5
Transfer of net unrealized loss from AFS to HTM		0
Ending balance	(20)	12
Securities | Held-to-Maturity Securities
Accumulated other comprehensive income (loss)
Beginning balance	5	0
Net unrealized loss, net of tax	0	0
Reclassifications out of AOCI	(1)
Transfer of net unrealized loss from AFS to HTM		5
Ending balance	4	5
Securities | Available-for-Sale Securities
Accumulated other comprehensive income (loss)
Beginning balance	0	8
Net unrealized loss, net of tax	17	9
Reclassifications out of AOCI	(4)
Transfer of net unrealized loss from AFS to HTM		(5)
Ending balance	13	12
Cash Flow Hedges
Accumulated other comprehensive income (loss)
Beginning balance	(3)	0
Net unrealized loss, net of tax	(44)	(5)
Reclassifications out of AOCI	10
Transfer of net unrealized loss from AFS to HTM		0
Ending balance	$ (37)	$ (5)