Total Equity and Other Comprehensive Income (Other Comprehensive Income) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Net unrealized gains (losses) on securities without an allowance for credit losses
Increase in net unrealized gains (losses) on securities	$ 661		$ 2,330
Less: Net gains (losses) realized as a yield adjustment reclassified to investment securities interest income	1		2
Less: Net gains (losses) realized on sales of securities reclassified to noninterest income	40		221
Net increase (decrease), pre-tax	620		2,107
Effect of income taxes	(143)		(484)
Net increase (decrease), after-tax	477		1,623
Net unrealized gains (losses) on securities with an allowance for credit losses
Increase in net unrealized gains (losses) on securities	(82)		(89)
Net increase (decrease), pre-tax	(82)		(89)
Effect of income taxes	18		20
Net increase (decrease), after-tax	(64)		(69)
Net Unrealized Gains Losses on Non Otti Securities [Abstract]
Increase in net unrealized gains (losses) on non-OTTI securities		$ 713		$ 1,353
Less: Net gains (losses) realized as a yield adjustment reclassified to investment securities in interest income		3		6
Less: Net gains (losses) realized on sales of non-OTTI securities reclassified to noninterest income		16		14
Net increase (decrease), pre-tax		694		1,333
Effect of income taxes		(159)		(306)
Net increase (decrease), after-tax		535		1,027
Net Unrealized Gains Losses On Otti Securities [Abstract]
Increase in net unrealized gains (losses) on OTTI securities				9
Net increase (decrease), pre-tax		0		9
Effect of income taxes				(2)
Net increase (decrease), after-tax		0		7
Net unrealized gains (losses) on cash flow hedge derivatives [Abstract]
Increase in net unrealized gains (losses) on cash flow hedge derivatives	115	246	945	354
Less: Net gains (losses) realized as a yield adjustment reclassified to loan interest income	102	(12)	144	(20)
Less: Net gains (losses) realized as a yield adjustment reclassified to investment securities interest income	1	1	3	2
Less: Net gains (losses) realized on sales of securities reclassified to noninterest income	0	3	1	18
Net increase (decrease), pre-tax	12	254	797	354
Effect of income taxes	(3)	(58)	(183)	(81)
Net increase (decrease), after-tax	9	196	614	273
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, before Tax [Abstract]
Net pension and other postretirement benefit plan activity	(20)	(89)	(10)	54
Amortization of actuarial loss (gain) reclassified to other noninterest expense	2	4	3	5
Amortization of prior service cost (credit) reclassified to other noninterest expense	1	1	2	2
Net increase (decrease), pre-tax	(17)	(84)	(5)	61
Effect of income taxes	4	19	1	(14)
Net increase (decrease), after-tax	(13)	(65)	(4)	47
Other Comprehensive Income Other Adjustments [Abstract]
Net investment hedge derivatives	5	32	80	14
Foreign currency translation adjustments and other	(3)	(27)	(70)	(4)
Net increase (decrease), pre-tax	2	5	10	10
Effect of income taxes	(1)	(7)	(19)	(4)
Net increase (decrease), after-tax	1	(2)	(9)	6
Other comprehensive income (loss), before tax and net of reclassifications into Net income	535	869	2,820	1,767
Total other comprehensive income (loss), tax effect	(125)	(205)	(665)	(407)
Other comprehensive income (loss), after tax and net of reclassifications into Net income	551	636	2,270	1,356
Continuing Operations
Other Comprehensive Income Other Adjustments [Abstract]
Other comprehensive income (loss), before tax and net of reclassifications into Net income	535	869	2,820	1,767
Total other comprehensive income (loss), tax effect	(125)	(205)	(665)	(407)
Other comprehensive income (loss), after tax and net of reclassifications into Net income	410	664	2,155	1,360
Discontinued Operations [Member]
Other Comprehensive Income Other Adjustments [Abstract]
Other comprehensive income (loss), after tax and net of reclassifications into Net income	$ 141	$ (28)	$ 115	$ (4)