Fair Value Measurements and Derivatives - Summary of Fixed-to-Fixed Cross-Currency Swaps (Details) € in Millions, $ in Millions		Mar. 31, 2018 USD ($)		Mar. 31, 2018 EUR (€)		Dec. 31, 2017 USD ($)		Dec. 31, 2017 EUR (€)		Apr. 04, 2017	Dec. 31, 2016 USD ($)
Senior Notes Due June 2026 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate	[1]	6.50%		6.50%		6.50%		6.50%
Senior Notes Due April 2025 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate		5.75%	[1]	5.75%	[1]	5.75%	[1]	5.75%	[1]	5.75%
Cash Flow Hedging [Member] | Senior Notes Due June 2026 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, amount of hedged item		$ 375									$ 375
Interest rate		6.50%		6.50%
Derivative, fixed interest rate		5.14%		5.14%
Cash Flow Hedging [Member] | Senior Notes Due April 2025 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, amount of hedged item		$ 400				$ 400
Interest rate		5.75%		5.75%
Derivative, fixed interest rate		3.85%		3.85%
Cash Flow Hedging [Member] | Intercompany Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, amount of hedged item | €				€ 281				€ 281
Interest rate		3.91%		3.91%
Currency Swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, Notional Amount		$ 1,121				$ 1,112
Currency Swap [Member] | United States of America, Dollars [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, Notional Amount		346
Currency Swap [Member] | Euro Member Countries, Euro [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, Notional Amount		775
Currency Swap [Member] | Cash Flow Hedging [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, Notional Amount		1,121
Currency Swap [Member] | Cash Flow Hedging [Member] | United States of America, Dollars [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, Notional Amount		346
Currency Swap [Member] | Cash Flow Hedging [Member] | Euro Member Countries, Euro [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, Notional Amount		775
Currency Swap [Member] | Cash Flow Hedging [Member] | Senior Notes Due June 2026 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, Notional Amount		$ 375		€ 338
Currency Swap [Member] | Cash Flow Hedging [Member] | Senior Notes Due June 2026 [Member] | United States of America, Dollars [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, fixed interest rate		6.50%		6.50%
Currency Swap [Member] | Cash Flow Hedging [Member] | Senior Notes Due June 2026 [Member] | Euro Member Countries, Euro [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, fixed interest rate		5.14%		5.14%
Currency Swap [Member] | Cash Flow Hedging [Member] | Senior Notes Due April 2025 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, Notional Amount		$ 400		€ 371
Derivative, fixed interest rate		3.85%		3.85%
Currency Swap [Member] | Cash Flow Hedging [Member] | Senior Notes Due April 2025 [Member] | United States of America, Dollars [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, fixed interest rate		5.75%		5.75%
Currency Swap [Member] | Cash Flow Hedging [Member] | Senior Notes Due April 2025 [Member] | Euro Member Countries, Euro [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, fixed interest rate		3.85%		3.85%
Currency Swap [Member] | Cash Flow Hedging [Member] | Intercompany Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, Notional Amount		$ 300		€ 281
Currency Swap [Member] | Cash Flow Hedging [Member] | Intercompany Notes [Member] | United States of America, Dollars [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, fixed interest rate		6.00%		6.00%
Currency Swap [Member] | Cash Flow Hedging [Member] | Intercompany Notes [Member] | Euro Member Countries, Euro [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, fixed interest rate		3.91%		3.91%

[1] In conjunction with the issuance of the April 2025 Notes we entered into 8-year fixed-to-fixed cross-currency swaps which have the effect of economically converting the April 2025 Notes to euro-denominated debt at a fixed rate of 3.850%. In conjunction with the issuance of the June 2026 Notes we entered into 10-year fixed-to-fixed cross-currency swaps which have the effect of economically converting the June 2026 Notes to euro-denominated debt at a fixed rate of 5.140%. See Note 14 for additional information.