Equity Activity in OCI (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Equity [Abstract]
Net income	$ 4,261	$ 2,773
Other comprehensive income (loss), net of tax effect:
Changes in net unrealized gains (losses) on AFS securities (net of tax of $15 and $5, respectively)	(57)	9
Reclassification adjustment for other-than-temporary impairment (OTTI) recognized in net income (net of tax of $0)	1	1
Reclassification adjustment for gains on AFS securities included in net income (net of tax of $70 and $1, respectively)	(264)	(2)
Other	(3)	(2)
Total other comprehensive income (loss)	(323)	6
Total comprehensive income	3,938	2,779
Other Comprehensive Income (Loss), Tax, Parenthetical Disclosures [Abstract]
Changes in net unrealized gains (losses) on AFS securities (net of tax of $15 and $5, respectively)	(15)	5
Reclassification adjustment for other-than-temporary impairment (OTTI) recognized in net income (net of tax of $0)	0	0
Reclassification adjustment for gains on AFS securities included in net income (net of tax of $70 and $1, respectively)	$ (70)	$ (1)