Total Equity and Other Comprehensive Income (Accumulated Other Comprehensive Income (Loss) Components) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Accumulated Other Comprehensive Income (Loss) [Line Items]
Equity, Beginning Balance	$ 53,879	$ 49,290	$ 54,041	$ 49,343
Other comprehensive income (loss), net of tax	173	551	(1,307)	2,270
Equity, Ending Balance	54,685	52,948	54,685	52,948
Continuing Operations
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), net of tax	173	410	(1,307)	2,155
Discontinued Operations
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), net of tax		141		115
Debt securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Equity, Beginning Balance	1,549	2,208	2,462	1,067
Other comprehensive income (loss), net of tax	35	413	(878)	1,554
Equity, Ending Balance	1,584	2,621	1,584	2,621
Cash flow hedge derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
Equity, Beginning Balance	67	881	659	276
Other comprehensive income (loss), net of tax	169	9	(423)	614
Equity, Ending Balance	236	890	236	890
Pension and  other postretirement benefit plan adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Equity, Beginning Balance	(322)	(399)	(345)	(408)
Other comprehensive income (loss), net of tax	(33)	(13)	(10)	(4)
Equity, Ending Balance	(355)	(412)	(355)	(412)
Other
Accumulated Other Comprehensive Income (Loss) [Line Items]
Equity, Beginning Balance	(4)	(31)	(6)	(21)
Other comprehensive income (loss), net of tax	2	1	4	(9)
Equity, Ending Balance	(2)	(30)	(2)	(30)
Total
Accumulated Other Comprehensive Income (Loss) [Line Items]
Equity, Beginning Balance	1,290	2,518	2,770	799
Other comprehensive income (loss), net of tax	173	551	(1,307)	2,270
Equity, Ending Balance	1,463	3,069	1,463	3,069
Total | Continuing Operations
Accumulated Other Comprehensive Income (Loss) [Line Items]
Equity, Beginning Balance	1,290	2,659	2,770	914
Other comprehensive income (loss), net of tax	173	410	(1,307)	2,155
Equity, Ending Balance	1,463	3,069	1,463	3,069
Total | Discontinued Operations
Accumulated Other Comprehensive Income (Loss) [Line Items]
Equity, Beginning Balance		(141)		(115)
Other comprehensive income (loss), net of tax		141		115
Equity, Ending Balance