Income Taxes - Items Accounting for Differences Between Income Taxes Computed at Federal Statutory Rate and Provision Recorded for Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Income taxes computed at the federal statutory rate (1)									$ 2,365	$ 1,332	$ 1,362
Effect of:
Tax impact of foreign earnings									119	1,178	(69)
State taxes, net of federal benefits									263	114	110
Tax credits									(419)	(220)	(119)
Stock-based compensation									(1,086)	(917)	189
Domestic production activities deduction									0	0	(94)
2017 Impact of U.S. Tax Act									(157)	(789)	0
Other, net									112	71	46
Provision for income taxes, net	$ 327	$ 508	$ 74	$ 287	$ 16	$ 58	$ 467	$ 229	1,197	769	$ 1,425
Excess tax benefits from stock-based compensation									$ 1,600	$ 1,300