Fair Value Measurements and Other Financial Instruments - Carrying Amounts and Estimated Fair Values of Debt (Parenthetical) (Detail)	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2014	Jun. 30, 2015
Term Loan A Due July 2017 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt maturity month and year, Term loan	2017-07	2017-07
Term Loan A Due July 2019 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt maturity month and year, Term loan	2019-07	2019-07
6.50% Senior Notes Due December 2020 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt interest rate	6.50%	6.50%
Debt maturity month and year, Senior notes	2020-12	2020-12
8.375% Senior Notes Due September 2021 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt interest rate	8.375%	8.375%	8.375%
Debt maturity month and year, Senior notes	2021-09	2021-09
4.875% Senior Notes due December 2022 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt interest rate	4.875%	4.875%
Debt maturity month and year, Senior notes	2022-12	2022-12
5.25% Senior Notes Due April 2023 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt interest rate	5.25%	5.25%
Debt maturity month and year, Senior notes	2023-04	2023-04
4.50% Senior Notes due September 2023 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt interest rate	4.50%	4.50%	4.50%
Debt maturity month and year, Senior notes	2023-09	2023-09
5.125% Senior Notes due December 2024 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt interest rate	5.125%	5.125%
Debt maturity month and year, Senior notes	2024-12	2024-12
5.50% Senior Notes due September 2025 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt interest rate	5.50%	5.50%	5.50%
Debt maturity month and year, Senior notes	2025-09	2025-09
6.875% Senior Notes Due July 2033 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt interest rate	6.875%	6.875%
Debt maturity month and year, Senior notes	2033-07	2033-07