Debt - Redemption Prices (Detail) - Senior notes	12 Months Ended
	Dec. 31, 2016
2023 Notes | Debt instrument redemption period one
Debt Instrument [Line Items]
Percentage of debt redemption price	102.375%
2023 Notes | Debt instrument redemption period two
Debt Instrument [Line Items]
Percentage of debt redemption price	101.583%
2023 Notes | Debt instrument redemption period three
Debt Instrument [Line Items]
Percentage of debt redemption price	100.792%
2023 Notes | Debt instrument redemption period four and thereafter
Debt Instrument [Line Items]
Percentage of debt redemption price	100.00%
2024 Notes | Debt instrument redemption period one
Debt Instrument [Line Items]
Percentage of debt redemption price	102.688%
2024 Notes | Debt instrument redemption period two
Debt Instrument [Line Items]
Percentage of debt redemption price	101.792%
2024 Notes | Debt instrument redemption period three
Debt Instrument [Line Items]
Percentage of debt redemption price	100.896%
2024 Notes | Debt instrument redemption period four and thereafter
Debt Instrument [Line Items]
Percentage of debt redemption price	100.00%
2025 Notes | Debt instrument redemption period one
Debt Instrument [Line Items]
Percentage of debt redemption price	102.625%
2025 Notes | Debt instrument redemption period two
Debt Instrument [Line Items]
Percentage of debt redemption price	101.75%
2025 Notes | Debt instrument redemption period three
Debt Instrument [Line Items]
Percentage of debt redemption price	100.875%
2025 Notes | Debt instrument redemption period four and thereafter
Debt Instrument [Line Items]
Percentage of debt redemption price	100.00%