Accumulated Other Comprehensive Income (Components of Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Other comprehensive income (loss) before tax
Net unrealized gain (loss)	$ 52	$ 21
Reclassification of net unrealized loss on securities transferred to held to maturity	227	0
Other reclassifications included in other revenue	(1)	0
Reclassification of net unrealized loss on securities transferred from available for sale	(227)	0
Amortization of amounts previously recorded upon transfer from available for sale	2	0
Other	(3)	1
Other comprehensive income (loss), before tax	50	22
Other comprehensive income (loss), tax effect
Net unrealized gain (loss)	(19)	(8)
Reclassification of net unrealized loss on securities transferred to held to maturity	(85)	0
Other reclassifications included in other revenue	0	0
Reclassification of net unrealized loss on securities transferred from available for sale	85	0
Amortization of amounts previously recorded upon transfer from available for sale	(1)	0
Other	1	0
Other comprehensive (loss) income, tax effect	(19)	(8)
Other comprehensive income (loss), net of tax
Net unrealized gain (loss)	33	13
Reclassification of net unrealized loss on securities transferred to held to maturity	142	0
Other reclassifications included in other revenue	(1)	0
Reclassification of net unrealized loss on securities transferred from available for sale	(142)	0
Amortization of amounts previously recorded upon transfer from available for sale	1	0
Other	(2)	1
Other comprehensive income (loss), net of tax	$ 31	$ 14