Income Taxes - Effective Tax Rate Reconciliation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Difference between income taxes computed at the U.S. federal statutory income tax rate and the income tax expense (benefit)
Federal income tax provision at statutory rate	$ 387	$ 392	$ 343
Federal income tax provision at statutory rate	35.00%	35.00%	35.00%
State taxes, net of federal benefit	$ 9	$ 5	$ 5
State taxes, net of federal benefit	1.00%	0.00%	0.00%
Research and development credits	$ (36)	$ (26)	$ (24)
Research and development credits	(3.00%)	(2.00%)	(2.00%)
Foreign rate differential	$ (239)	$ (228)	$ (245)
Foreign rate differential	(22.00%)	(20.00%)	(25.00%)
Change in tax reserves	$ 210	$ 136	$ 128
Change in tax reserves	19.00%	12.00%	13.00%
Net operating loss tax attribute assumed from the Purchase Transaction	$ (114)	$ (63)	$ (52)
Net operating loss tax attribute assumed from the Purchase Transaction	(10.00%)	(6.00%)	(5.00%)
Excess tax benefit related to share-based payments	$ (81)	$ 0	$ 0
Excess tax benefit related to share-based payments	(7.00%)	(0.00%)	(0.00%)
Other	$ 4	$ 13	$ (9)
Other	0.00%	1.00%	(1.00%)
Income tax expense	$ 140	$ 229	$ 146
Income tax expense	13.00%	20.00%	15.00%