Debt Facilities - Summary of Senior Notes Redemption Price Percentage (Detail) - Senior Notes	12 Months Ended
	Dec. 31, 2017
5.375% Senior Notes due 2022 | Early Equity Redemption Price
Debt Instrument, Redemption [Line Items]
Redemption price, percentage	105.375%
5.375% Senior Notes due 2022 | First Scheduled Redemption Price
Debt Instrument, Redemption [Line Items]
Redemption price, percentage	104.031%
5.375% Senior Notes due 2022 | Second Year Redemption Price
Debt Instrument, Redemption [Line Items]
Redemption price, percentage	102.688%
5.375% Senior Notes due 2022 | Third Year Redemption Price
Debt Instrument, Redemption [Line Items]
Redemption price, percentage	101.344%
5.375% Senior Notes due 2022 | Fourth Year (if scheduled) Redemption Price
Debt Instrument, Redemption [Line Items]
Redemption price, percentage	100.00%
5.375% Senior Notes due 2023 | Early Equity Redemption Price
Debt Instrument, Redemption [Line Items]
Redemption price, percentage	105.375%
5.375% Senior Notes due 2023 | First Scheduled Redemption Price
Debt Instrument, Redemption [Line Items]
Redemption price, percentage	102.688%
5.375% Senior Notes due 2023 | Second Year Redemption Price
Debt Instrument, Redemption [Line Items]
Redemption price, percentage	101.792%
5.375% Senior Notes due 2023 | Third Year Redemption Price
Debt Instrument, Redemption [Line Items]
Redemption price, percentage	100.896%
5.375% Senior Notes due 2023 | Fourth Year (if scheduled) Redemption Price
Debt Instrument, Redemption [Line Items]
Redemption price, percentage	100.00%
5.750% Senior Notes due 2025 | Early Equity Redemption Price
Debt Instrument, Redemption [Line Items]
Redemption price, percentage	105.75%
5.750% Senior Notes due 2025 | First Scheduled Redemption Price
Debt Instrument, Redemption [Line Items]
Redemption price, percentage	102.875%
5.750% Senior Notes due 2025 | Second Year Redemption Price
Debt Instrument, Redemption [Line Items]
Redemption price, percentage	101.917%
5.750% Senior Notes due 2025 | Third Year Redemption Price
Debt Instrument, Redemption [Line Items]
Redemption price, percentage	100.958%
5.750% Senior Notes due 2025 | Fourth Year (if scheduled) Redemption Price
Debt Instrument, Redemption [Line Items]
Redemption price, percentage	100.00%
2.875% Euro Senior Notes due 2025 | Early Equity Redemption Price
Debt Instrument, Redemption [Line Items]
Redemption price, percentage	102.875%
2.875% Euro Senior Notes due 2025 | First Scheduled Redemption Price
Debt Instrument, Redemption [Line Items]
Redemption price, percentage	101.438%
2.875% Euro Senior Notes due 2025 | Second Year Redemption Price
Debt Instrument, Redemption [Line Items]
Redemption price, percentage	100.719%
2.875% Euro Senior Notes due 2025 | Third Year Redemption Price
Debt Instrument, Redemption [Line Items]
Redemption price, percentage	100.00%
5.875% Senior Notes due 2026 | Early Equity Redemption Price
Debt Instrument, Redemption [Line Items]
Redemption price, percentage	105.875%
5.875% Senior Notes due 2026 | First Scheduled Redemption Price
Debt Instrument, Redemption [Line Items]
Redemption price, percentage	102.938%
5.875% Senior Notes due 2026 | Second Year Redemption Price
Debt Instrument, Redemption [Line Items]
Redemption price, percentage	101.958%
5.875% Senior Notes due 2026 | Third Year Redemption Price
Debt Instrument, Redemption [Line Items]
Redemption price, percentage	100.979%
5.875% Senior Notes due 2026 | Fourth Year (if scheduled) Redemption Price
Debt Instrument, Redemption [Line Items]
Redemption price, percentage	100.00%
2.875% Euro Senior Notes due 2026 | Early Equity Redemption Price
Debt Instrument, Redemption [Line Items]
Redemption price, percentage	102.875%
2.875% Euro Senior Notes due 2026 | First Scheduled Redemption Price
Debt Instrument, Redemption [Line Items]
Redemption price, percentage	101.438%
2.875% Euro Senior Notes due 2026 | Second Year Redemption Price
Debt Instrument, Redemption [Line Items]
Redemption price, percentage	100.719%
2.875% Euro Senior Notes due 2026 | Third Year Redemption Price
Debt Instrument, Redemption [Line Items]
Redemption price, percentage	100.00%
5.375% Senior Notes due 2027 | Early Equity Redemption Price
Debt Instrument, Redemption [Line Items]
Redemption price, percentage	105.375%
5.375% Senior Notes due 2027 | First Scheduled Redemption Price
Debt Instrument, Redemption [Line Items]
Redemption price, percentage	102.688%
5.375% Senior Notes due 2027 | Second Year Redemption Price
Debt Instrument, Redemption [Line Items]
Redemption price, percentage	101.792%
5.375% Senior Notes due 2027 | Third Year Redemption Price
Debt Instrument, Redemption [Line Items]
Redemption price, percentage	100.896%
5.375% Senior Notes due 2027 | Fourth Year (if scheduled) Redemption Price
Debt Instrument, Redemption [Line Items]
Redemption price, percentage	100.00%