Fair Value Measurements - Narrative (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($) contract	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jun. 30, 2017 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gains and losses on derivative financial instruments recognized in other non-operating items (less than)	$ 1	$ 1
Fair value of earn-out liability			$ 14		$ 14
Other operating income from earn out liability adjustment			$ 13
Fair value of contingent consideration	$ 0
Foreign exchange swaps | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Maturity period of swap contracts	6 months
Foreign exchange swaps | Maturity Beyond Six Months
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of foreign currency derivatives held | contract	0
Foreign exchange forward contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset (Other current/non current assets)	$ 98			$ 103
Derivative Liability (Other current/non current liabilities)	1
Fair Value Measured at Net Asset Value Per Share
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment	$ 8			$ 8		$ 15