Accumulated Other Comprehensive Income (Components of Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Other comprehensive income (loss) before tax
Net unrealized gain (loss)	$ 5,151	$ 227
Other reclassifications included in other revenue	0	(1)
Amortization of amounts previously recorded upon transfer to held to maturity from available for sale	0	12
Other comprehensive income (loss), before tax	5,151	238
Tax Effect
Net unrealized gain (loss)	(1,244)	(54)
Other reclassifications included in other revenue	0	0
Amortization of amounts previously recorded upon transfer to held to maturity from available for sale	0	(3)
Other comprehensive income (loss)	(1,244)	(57)
Net of Tax
Net unrealized gain (loss)	3,907	173
Other reclassifications included in other revenue	0	(1)
Amortization of amounts previously recorded upon transfer from available for sale	0	9
Other comprehensive income (loss), net of tax	$ 3,907	$ 181