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Long-Term Debt - Summary of Long-Term Debt (Detail) - USD ($) $ in Thousands | Sep. 30, 2018 | Dec. 31, 2017
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Debt Instrument [Line Items] |  |
Total long-term debt | $ 647,748 | $ 483,330
Less current portion | (10,904) | (11,298)
Unamortized deferred issuance costs | (1,438) | (1,934)
Long-term debt, net of current portion | 635,406 | 470,098
Revolving Credit Facility, Due Mar. 2020 [Member] |  |
Debt Instrument [Line Items] |  |
Total long-term debt | 345,962 | 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 | 6,201 | 7,710
2.05% Term Loan, Due Mar. 2023 [Member] |  |
Debt Instrument [Line Items] |  |
Total long-term debt | 27,802 | 33,607
1.30% Term Loan, Due Jun. 2023 [Member] |  |
Debt Instrument [Line Items] |  |
Total long-term debt | 7,855 | 9,423
1.55% Term Loan, Due Sep. 2025 [Member] |  |
Debt Instrument [Line Items] |  |
Total long-term debt | $ 9,928 | $ 11,390

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