Other Comprehensive Income, Cumulative OCI Balances (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Investment securities:
Cumulative other comprehensive income, Investment securities, beginning of period	$ 2,812	$ 3,509	$ 1,813	$ 4,926
Net unrealized gains (losses) arising during the period	80	(293)	1,540	(1,238)
Amounts reclassified from accumulated other comprehensive income	(120)	(279)	(625)	(602)
Net change, Net of tax	(40)	(572)	915	(1,840)
Less: Other comprehensive income (loss) from noncontrolling interests	19	(20)	(25)	129
Cumulative other comprehensive income, Investment securities, end of period	2,753	2,957	2,753	2,957
Derivatives and hedging activities:
Cumulative other comprehensive income, Derivatives and hedging activities, beginning of period	2,199	310	620	333
Net unrealized gains (losses) arising during the period	(277)	1,102	1,627	1,391
Amounts reclassified from accumulated other comprehensive income	(163)	(183)	(488)	(495)
Net change, Net of tax	(440)	919	1,139	896
Less: Other comprehensive income from noncontrolling interests	0	0	0	0
Cumulative other comprehensive income, Derivatives and hedging activities, end of period	1,759	1,229	1,759	1,229
Defined benefit plans adjustments:
Cumulative other comprehensive loss, Defined benefit plans adjustment, beginning of period	(1,921)	(1,665)	(1,951)	(1,703)
Net unrealized losses arising during the period	(279)	0	(296)	(7)
Amounts reclassified from accumulated other comprehensive income	25	19	72	64
Net change, Net of tax	(254)	19	(224)	57
Less: Other comprehensive income from noncontrolling interests	0	0	0	0
Cumulative other comprehensive loss, Defined benefit plans adjustment, end of period	(2,175)	(1,646)	(2,175)	(1,646)
Foreign currency translation adjustments:
Cumulative other comprehensive loss, Foreign currency translation adjustments, beginning of period	(142)	(86)	(185)	(38)
Net unrealized gains (losses) arising during the period	(11)	(67)	33	(117)
Amounts reclassified from accumulated other comprehensive income	0	0	0	0
Net change, Net of tax	(11)	(67)	33	(117)
Less: Other comprehensive income (loss) from noncontrolling interests	0	(2)	1	(4)
Cumulative other comprehensive loss, Foreign currency translation adjustments, end of period	(153)	(151)	(153)	(151)
Cumulative other comprehensive income, beginning of period	2,948	2,068	297	3,518
Net unrealized gains (losses) arising during the period	(487)	742	2,904	29
Amounts reclassified from accumulated other comprehensive income	(258)	(443)	(1,041)	(1,033)
Other comprehensive income (loss), net of tax	(745)	299	1,863	(1,004)
Less: Other comprehensive income (loss) from noncontrolling interests, net of tax	19	(22)	(24)	125
Cumulative other comprehensive income, end of period	$ 2,184	$ 2,389	$ 2,184	$ 2,389