Debt - Summary of Outstanding Debt (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Total debt	$ 1,655,000	$ 1,829,750
Less: current portion	16,575	19,075
Total long-term debt, gross (less current portion)	1,638,425	1,810,675
Total long-term debt, gross (less current portion)	1,638,425	1,810,675
Less: deferred financing costs, net	15,437	20,232
Total long-term debt, net (less current portion)	1,622,988	1,790,443
Bank Credit Facility [Member]
Debt Instrument [Line Items]
Total debt	1,155,000	1,329,750
5 1/2% Senior Notes Due 2021 [Member]
Debt Instrument [Line Items]
Total debt	200,000	200,000
6 3/8% Senior Notes Due 2023 [Member]
Debt Instrument [Line Items]
Total debt	$ 300,000	$ 300,000