Long-Term Debt - Summary of Long-Term Debt (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Total long-term debt	$ 483,330	$ 375,161
Less current portion	(11,298)	(8,961)
Unamortized deferred issuance costs	(1,934)	(2,553)
Long-term debt, net of current portion	470,098	363,647
Revolving Credit Facility, Due Mar. 2020 [Member]
Debt Instrument [Line Items]
Total long-term debt	171,200	61,595
5.375% Notes, Due Oct. 2020 [Member]
Debt Instrument [Line Items]
Total long-term debt	250,000	250,000
Long-term debt, net of current portion	250,000	250,000
2.40% Term Loan, Due Jun. 2022 [Member]
Debt Instrument [Line Items]
Total long-term debt	7,710	8,282
2.05% Term Loan, Due Mar. 2023 [Member]
Debt Instrument [Line Items]
Total long-term debt	33,607	35,163
1.30% Term Loan, Due Jun. 2023 [Member]
Debt Instrument [Line Items]
Total long-term debt	9,423	9,788
1.55% Term Loan, Due Sep. 2025 [Member]
Debt Instrument [Line Items]
Total long-term debt	$ 11,390	$ 10,333