Long-Term Debt - Summary of Long-Term Debt (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Total long-term debt	$ 507,517	$ 483,330
Less current portion	(11,607)	(11,298)
Unamortized deferred issuance costs	(1,779)	(1,934)
Long-term debt, net of current portion	494,131	470,098
Revolving Credit Facility, Due Mar. 2020 [Member]
Debt Instrument [Line Items]
Total long-term debt	196,588	171,200
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	7,481	7,710
2.05% Term Loan, Due Mar. 2023 [Member]
Debt Instrument [Line Items]
Total long-term debt	32,883	33,607
1.30% Term Loan, Due Jun. 2023 [Member]
Debt Instrument [Line Items]
Total long-term debt	9,241	9,423
1.55% Term Loan, Due Sep. 2025 [Member]
Debt Instrument [Line Items]
Total long-term debt	$ 11,324	$ 11,390