Schedule of Debt Outstanding (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Total debt	$ 1,459,000	$ 1,455,000
Unamortized debt issuance costs	(11,813)	(9,831)
Current portion of long-term debt	(10,000)	(10,000)
Long-term debt, net	1,437,187	1,435,169
Term Loan Due in July 2020
Debt Instrument [Line Items]
Total debt	85,000	95,000
Unamortized debt issuance costs	(300)	(400)
Senior Notes 4.625% Due 2023
Debt Instrument [Line Items]
Total debt	350,000	350,000
Unamortized debt issuance costs	(3,300)	(3,900)
Senior Notes 4.125% Due 2020
Debt Instrument [Line Items]
Total debt	325,000	325,000
Unamortized debt issuance costs	(1,900)	(2,700)
Senior Notes 5.0% Due 2022
Debt Instrument [Line Items]
Total debt	250,000	250,000
Unamortized debt issuance costs	(2,300)	(2,800)
Senior Notes 4.75% Due 2027
Debt Instrument [Line Items]
Total debt	250,000
Unamortized debt issuance costs	(4,000)
Revolving Credit Facility | $900.0 Million Revolving Credit Facility
Debt Instrument [Line Items]
Total debt	$ 199,000	$ 435,000