Total Equity and Other Comprehensive Income (Accumulated Other Comprehensive Income (Loss) Components) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Accumulated Other Comprehensive Income (Loss) [Line Items]
Equity, Beginning Balance	$ 54,041	$ 49,343
Other comprehensive income (loss), net of tax	(1,480)	1,719
Equity, Ending Balance	53,879	49,290
Continuing Operations
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), net of tax	(1,480)	1,745
Discontinued Operations
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), net of tax		(26)
Debt securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Equity, Beginning Balance	2,462	1,067
Other comprehensive income (loss), net of tax	(913)	1,141
Equity, Ending Balance	1,549	2,208
Cash flow hedge derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
Equity, Beginning Balance	659	276
Other comprehensive income (loss), net of tax	(592)	605
Equity, Ending Balance	67	881
Pension and  other postretirement benefit plan adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Equity, Beginning Balance	(345)	(408)
Other comprehensive income (loss), net of tax	23	9
Equity, Ending Balance	(322)	(399)
Other
Accumulated Other Comprehensive Income (Loss) [Line Items]
Equity, Beginning Balance	(6)	(21)
Other comprehensive income (loss), net of tax	2	(10)
Equity, Ending Balance	(4)	(31)
Total
Accumulated Other Comprehensive Income (Loss) [Line Items]
Equity, Beginning Balance	2,770	799
Other comprehensive income (loss), net of tax	(1,480)	1,719
Equity, Ending Balance	1,290	2,518
Total | Continuing Operations
Accumulated Other Comprehensive Income (Loss) [Line Items]
Equity, Beginning Balance	2,770	914
Other comprehensive income (loss), net of tax	(1,480)	1,745
Equity, Ending Balance	1,290	2,659
Total | Discontinued Operations
Accumulated Other Comprehensive Income (Loss) [Line Items]
Equity, Beginning Balance		(115)
Other comprehensive income (loss), net of tax		(26)
Equity, Ending Balance		$ (141)