Total Equity and Other Comprehensive Income (Other Comprehensive Income) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, before Tax [Abstract]
Net unrealized gains (losses) on securities, pre-tax	$ (6,318)	$ (1,181)
Less: Net realized gains (losses) reclassified to earnings	(3)	13
Net increase (decrease), pre-tax	(6,315)	(1,194)
Other Comprehensive Income (Loss), Available-for-sale Securities, before Reclassification Adjustments, Tax [Abstract]
Net unrealized gains (losses) on securities, tax effect	1,489	278
Less: Net realized gains (losses) reclassified to earnings, tax effect	1	(3)
Effect of income taxes	1,488	281
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, After Reclassification Adjustments, after Tax [Abstract]
Net unrealized gains (losses) on securities, after tax	(4,829)	(903)
Less: Net realized gains (losses) reclassified to earnings, after tax	(2)	10
Net increase (decrease), after-tax	(4,827)	(913)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification, before Tax [Abstract]
Net unrealized gains (losses) on cash flow hedges, pre-tax	(1,656)	(640)
Less: Net realized gains (losses) reclassified to earnings, pre-tax	102	135
Net increase (decrease), pre-tax	(1,758)	(775)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification, Tax [Abstract]
Net unrealized gains (losses) on cash flow hedges, tax effect	390	151
Less: Net realized gains (losses) reclassified to earnings, tax effect	(24)	(32)
Effect of income taxes	414	183
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax [Abstract]
Net unrealized gains (losses) on cash flow hedges, after tax	(1,266)	(489)
Less: Net realized gains (losses) reclassified to earnings, after tax	78	103
Net increase (decrease), after-tax	(1,344)	(592)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), after Reclassification Adjustment, before Tax [Abstract]
Net pension and other postretirement benefit plan activity and other reclassified to earnings, pre-tax	54	30
Net increase (decrease), pre-tax	54	30
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax [Abstract]
Net pension and other postretirement benefit plan activity and other reclassified to earnings, tax effect	(13)	(7)
Effect of income taxes	(13)	(7)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax [Abstract]
Net pension and other postretirement benefit plan activity and other reclassified to earnings, after-tax	41	23
Net increase (decrease), after-tax	41	23
Other Comprehensive Income Other Adjustments [Abstract]
Net unrealized gains (losses) on other transactions, pre-tax	(3)	1
Net increase (decrease), pre-tax	(3)	1
Net unrealized gains (losses) on other transactions, tax effect	(7)	1
Effect of income taxes	(7)	1
Net unrealized gains (losses) on other transactions, after tax	(10)	2
Net increase (decrease), after-tax	(10)	2
Other comprehensive income (loss), before tax and net of reclassifications into Net income	(8,022)	(1,938)
Total other comprehensive income (loss), tax effect	1,882	458
Other comprehensive income (loss), after tax and net of reclassifications into Net income	$ (6,140)	$ (1,480)