Debt and Financing Arrangements - Summary of Reconciliation of Debt (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Capital Leases, described below	$ 105,000	$ 89,916
Total debt	155,000	132,916
Less: current portion of long-term debt	16,839	14,083
Long-term debt, less current portion	138,161	118,833
Restated Credit Agreement [Member] \| Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Credit Agreement with Banks, described below	$ 50,000	$ 43,000

Amount equal to the present value (the principal) at the beginning of the lease term of minimum lease payments during the lease term (excluding that portion of the payments representing executory costs such as insurance, maintenance, and taxes to be paid by the lessor, together with any profit thereon) net of payments or other amounts applied to the principal through the balance sheet date.

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