Income Taxes (Federal Statutory) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Taxes [Line Items]
Federal tax at statutory rate	$ (3,569)	$ (3,201)	$ (5,374)
State income taxes, net of federal benefit	(306)	(212)	(299)
Foreign income taxed at different rates	(126)	(147)	(70)
Nontaxable income attributable to noncontrolling interests	51	20	45
Other adjustments	40	138	229
Excess tax benefits recognized on share-based compensation	196	75	297
Tax legislation	31	120	12,682
Income tax (expense) benefit	(3,673)	(3,380)	7,569
Adjustments to uncertain and effectively settled tax positions, net [Member]
Income Taxes [Line Items]
Other adjustments	(3)	(144)	62
Accrued interest on uncertain and effectively settled tax positions, net [Member]
Income Taxes [Line Items]
Other adjustments	$ 13	$ (29)	$ (3)