Equity Activity in OCI (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Equity [Abstract]
Net income	$ 3,200	$ 2,946	$ 5,973	$ 4,082
Other comprehensive loss, net of tax effect:
Changes in net unrealized gains (losses) on AFS securities (net of tax of $6 and $27, respectively, for the three months ended and net of tax of $11 and $21, respectively, for the six months ended)	11	50	20	(39)
Reclassification adjustment for OTTI recognized in net income (net of tax of $0 and $1, respectively, for the three months ended and net of tax of $0 and $11, respectively, for the six months ended)	0	1	1	20
Reclassification adjustment for gains on AFS securities included in net income (net of tax of $50 and $68, respectively, for the three months ended and net of tax of $51 and $137, respectively, for the six months ended)	(92)	(126)	(94)	(254)
Other	(2)	(2)	(4)	(4)
Total other comprehensive loss	(83)	(77)	(77)	(277)
Total comprehensive income	3,117	2,869	5,896	3,805
Other Comprehensive Income (Loss), Tax, Parenthetical Disclosures [Abstract]
Changes in net unrealized gains (losses) on AFS securities (net of tax of $6 and $27, respectively, for the three months ended and net of tax of $11 and $21, respectively, for the six months ended)	6	27	11	(21)
Reclassification adjustment for OTTI recognized in net income (net of tax of $0 and $1, respectively, for the three months ended and net of tax of $0 and $11, respectively, for the six months ended)	0	1	0	11
Reclassification adjustment for gains on AFS securities included in net income (net of tax of $50 and $68, respectively, for the three months ended and net of tax of $51 and $137, respectively, for the six months ended)	$ (50)	$ (68)	$ (51)	$ (137)