Total Equity and Other Comprehensive Income (Accumulated Other Comprehensive Income (Loss) Components) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Accumulated Other Comprehensive Income (Loss) [Line Items]
Equity, Beginning Balance	$ 54,685	$ 52,948	$ 54,041	$ 49,343
Other comprehensive income (loss), net of tax	(384)	(72)	(1,691)	2,198
Equity, Ending Balance	56,297	53,310	56,297	53,310
Continuing Operations
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), net of tax	(384)	(72)	(1,691)	2,083
Discontinued Operations
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), net of tax				115
Debt securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Equity, Beginning Balance	1,584	2,621	2,462	1,067
Other comprehensive income (loss), net of tax	(246)	8	(1,124)	1,562
Equity, Ending Balance	1,338	2,629	1,338	2,629
Cash flow hedge derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
Equity, Beginning Balance	236	890	659	276
Other comprehensive income (loss), net of tax	(133)	(92)	(556)	522
Equity, Ending Balance	103	798	103	798
Pension and  other postretirement benefit plan adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Equity, Beginning Balance	(355)	(412)	(345)	(408)
Other comprehensive income (loss), net of tax	2	2	(8)	(2)
Equity, Ending Balance	(353)	(410)	(353)	(410)
Other
Accumulated Other Comprehensive Income (Loss) [Line Items]
Equity, Beginning Balance	(2)	(30)	(6)	(21)
Other comprehensive income (loss), net of tax	(7)	10	(3)	1
Equity, Ending Balance	(9)	(20)	(9)	(20)
Total
Accumulated Other Comprehensive Income (Loss) [Line Items]
Equity, Beginning Balance	1,463	3,069	2,770	799
Other comprehensive income (loss), net of tax	(384)	(72)	(1,691)	2,198
Equity, Ending Balance	1,079	2,997	1,079	2,997
Total | Continuing Operations
Accumulated Other Comprehensive Income (Loss) [Line Items]
Equity, Beginning Balance	1,463	3,069	2,770	914
Other comprehensive income (loss), net of tax	(384)	(72)	(1,691)	2,083
Equity, Ending Balance	1,079	2,997	1,079	2,997
Total | Discontinued Operations
Accumulated Other Comprehensive Income (Loss) [Line Items]
Equity, Beginning Balance				(115)
Other comprehensive income (loss), net of tax				115
Equity, Ending Balance