Income Taxes - Income Tax Reconciliation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Federal statutory rate	35.00%	35.00%	35.00%
Provision at statutory rate	$ 1,278	$ 843	$ 881
Prior year foreign earnings no longer considered indefinitely reinvested	0	0	2,991
Foreign income taxed at different rates	(346)	(399)	(432)
Change in valuation allowance	0	1	(142)
Stock-based compensation	24	23	22
State taxes, net of federal benefit	55	20	42
Research and other tax credits	(16)	(27)	(14)
Tax basis step-up resulting from realignment	(4,621)	0	0
Other	(8)	(2)	32
Income tax expense (benefit)	$ (3,634)	$ 459	$ 3,380