Fair Value Measurements - Carrying Value and Estimated Fair Values of Outstanding Debt (Detail) € in Millions, $ in Millions	Sep. 30, 2017 USD ($)	Sep. 30, 2017 EUR (€)	Dec. 31, 2016 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior notes, carrying value	$ 1,531.2		$ 848.5
10.000% Senior Notes Due in 2021 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior notes, carrying value	271.1		384.2
5.500% Senior Notes Due in 2024 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior notes, carrying value	521.3	€ 450.0	464.3
5.500% Senior Notes Due in 2025 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior notes, carrying value	738.8
Level 1 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Outstanding debt, fair value	1,631.2		889.2
Level 1 [Member] | 10.000% Senior Notes Due in 2021 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Outstanding debt, fair value	264.4		383.7
Level 1 [Member] | 5.500% Senior Notes Due in 2024 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Outstanding debt, fair value	584.9		$ 505.5
Level 1 [Member] | 5.500% Senior Notes Due in 2025 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Outstanding debt, fair value	$ 781.9