Income Taxes (Income Tax Reconciliation) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income before income taxes
United States									$ 3,267	$ 5,716	$ 2,799
Foreign									911	1,729	756
Income before income taxes	$ 1,066	$ 943	$ 1,829	$ 340	$ 2,918	$ 1,975	$ 1,835	$ 717	$ 4,178	$ 7,445	$ 3,555
Percentage of Income Before Income Taxes
United States									78.20%	76.80%	78.70%
Foreign									21.80%	23.20%	21.30%
Income before income taxes									100.00%	100.00%	100.00%
Income Tax Expense (Benefit), Income Tax Reconciliation
Federal statutory income tax									$ 877	$ 1,563	$ 1,244
State income tax, net of federal benefit									92	155	79
Tax Cuts and Jobs Act									(42)	36	(2,721)
Foreign rate differential									(31)	(3)	(137)
Noncontrolling interests									(61)	(58)	(46)
Change in valuation allowance									14	(20)	(4)
Other									(48)	(101)	(108)
Income tax expense									$ 801	$ 1,572	$ (1,693)
Effective Income Tax Rate, Tax Rate Reconciliation
Federal statutory income tax									21.00%	21.00%	35.00%
State income tax, net of federal benefit									2.20%	2.10%	2.20%
Tax Cuts and Jobs Act									(1.00%)	0.50%	(76.50%)
Foreign rate differential									(0.70%)	0.00%	(3.90%)
Noncontrolling interests									(1.50%)	(0.80%)	(1.30%)
Change in valuation allowance									0.30%	(0.30%)	(0.10%)
Other									(1.10%)	(1.40%)	(3.00%)
Effective income tax rate									19.20%	21.10%	(47.60%)