Accumulated Other Comprehensive Income (Components of Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Other comprehensive income (loss) before tax
Net unrealized gain (loss)	$ 51	$ (43)	$ 496	$ (184)
Other reclassifications included in other revenue	(1)	0	(5)	0
Amortization of amounts previously recorded upon transfer to held to maturity from available for sale	10	8	30	26
Other comprehensive income (loss), before tax	60	(35)	521	(158)
Tax Effect
Net unrealized gain (loss)	(12)	11	(119)	45
Other reclassifications included in other revenue	0	0	1	0
Amortization of amounts previously recorded upon transfer to held to maturity from available for sale	(3)	(2)	(7)	(6)
Other comprehensive income (loss)	(15)	9	(125)	39
Net of Tax
Net unrealized gain (loss)	39	(32)	377	(139)
Other reclassifications included in other revenue	(1)	0	(4)	0
Amortization of amounts previously recorded upon transfer from available for sale	7	6	23	20
Other comprehensive income (loss), net of tax	$ 45	$ (26)	$ 396	$ (119)