Total Equity and Other Comprehensive Income (Accumulated Other Comprehensive Income (Loss) Components) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Equity, Beginning Balance	$ 52,948		$ 49,343	$ 47,770
Other comprehensive income (loss), net of tax	(72)	$ 206	2,198	1,562
Equity, Ending Balance	53,310	49,455	53,310	49,455
Continuing Operations
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), net of tax	(72)	225	2,083	1,585
Discontinued Operations
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), net of tax		(19)	115	(23)
Debt securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Equity, Beginning Balance	2,621	954	1,067	(80)
Other comprehensive income (loss), net of tax	8	165	1,562	1,199
Equity, Ending Balance	2,629	1,119	2,629	1,119
Net unrealized gains (losses) on cash flow hedge derivatives [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Equity, Beginning Balance	890	320	276	47
Other comprehensive income (loss), net of tax	(92)	61	522	334
Equity, Ending Balance	798	381	798	381
Pension and other postretirement benefit plan adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Equity, Beginning Balance	(412)	(483)	(408)	(530)
Other comprehensive income (loss), net of tax	2	2	(2)	49
Equity, Ending Balance	(410)	(481)	(410)	(481)
Other [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Equity, Beginning Balance	(30)	(37)	(21)	(43)
Other comprehensive income (loss), net of tax	10	(3)	1	3
Equity, Ending Balance	(20)	(40)	(20)	(40)
Total [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Equity, Beginning Balance	3,069	631	799	(725)
Other comprehensive income (loss), net of tax	(72)	206	2,198	1,562
Equity, Ending Balance	2,997	837	2,997	837
Total [Member] | Continuing Operations
Accumulated Other Comprehensive Income (Loss) [Line Items]
Equity, Beginning Balance	3,069	754	914	(606)
Other comprehensive income (loss), net of tax	(72)	225	2,083	1,585
Equity, Ending Balance	2,997	979	2,997	979
Total [Member] | Discontinued Operations
Accumulated Other Comprehensive Income (Loss) [Line Items]
Equity, Beginning Balance	0	(123)	(115)	(119)
Other comprehensive income (loss), net of tax		(19)	115	(23)
Equity, Ending Balance	$ 0	$ (142)	$ 0	$ (142)