Equity Activity in OCI (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Equity [Abstract]
Net income	$ 3,023	$ 3,196	$ 8,996	$ 7,278
Other comprehensive income (loss), net of tax effect:
Changes in net unrealized gains (losses) on AFS securities (net of tax of $25 and $18, respectively, for the three months ended and net of tax of $36 and $3, respectively, for the nine months ended)	47	33	67	(6)
Reclassification adjustment for OTTI recognized in net income (net of tax of $1 and $1, respectively, for the three months ended and net of tax of $1 and $12, respectively, for the nine months ended)	1	2	2	22
Reclassification adjustment for gains on AFS securities included in net income (net of tax of $11 and $129, respectively, for the three months ended and net of tax of $62 and $266, respectively, for the nine months ended)	(21)	(240)	(115)	(494)
Other	(2)	(2)	(6)	(6)
Total other comprehensive income (loss)	25	(207)	(52)	(484)
Total comprehensive income	3,048	2,989	8,944	6,794
Other Comprehensive Income (Loss), Tax, Parenthetical Disclosures [Abstract]
Changes in net unrealized gains (losses) on AFS securities (net of tax of $25 and $18, respectively, for the three months ended and net of tax of $36 and $3, respectively, for the nine months ended)	25	18	36	3
Reclassification adjustment for OTTI recognized in net income (net of tax of $1 and $1, respectively, for the three months ended and net of tax of $1 and $12, respectively, for the nine months ended)	1	1	1	12
Reclassification adjustment for gains on AFS securities included in net income (net of tax of $11 and $129, respectively, for the three months ended and net of tax of $62 and $266, respectively, for the nine months ended)	$ 11	$ 129	$ 62	$ 266