Income Taxes - Reconciliation of Beginning and Ending Balances of Total Amounts of Gross Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	$ 95	$ 130	$ 53
International operation acquired amounts	0	0	71
Additions to prior years' tax positions	0	1	0
Reductions to prior years' tax positions	(7)	(12)	(1)
Additions to current year tax positions	1	7	12
Reductions in tax positions due to lapse of statutory limitations	(16)	(6)	(3)
Settlements	(2)	(20)	(1)
Foreign currency translation	(10)	(5)	(1)
Ending balance	$ 61	$ 95	$ 130