Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net Income	$ 783	$ 564	[1]
Change in net unrealized gain (loss) on available for sale securities:
Net unrealized gain (loss)	(108)	52
Reclassification of net unrealized loss transferred to held to maturity	0	227
Other reclassifications included in other revenue	0	(1)
Change in net unrealized gain (loss) on held to maturity securities:
Reclassification of net unrealized loss transferred from available for sale	0	(227)
Amortization of amounts previously recorded upon transfer from available for sale	9	2
Other	0	(3)
Other comprehensive income (loss), before tax	(99)	50
Income tax effect	24	(19)
Other comprehensive income (loss), net of tax	(75)	31
Comprehensive Income	$ 708	$ 595

[1] Adjusted for the retrospective adoption of ASU 2016-18. See Note 2.