Significant Accounting Policies and Recently Issued Accounting Standards - Accrued Liabilities Related to Insurance Programs (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule Of Accrued Liabilities [Line Items]
Insurance liability	$ 26,999	$ 33,144
Automobile and general liability insurance [Member]
Schedule Of Accrued Liabilities [Line Items]
Insurance liability	14,410	21,219
Workers' compensation [Member]
Schedule Of Accrued Liabilities [Line Items]
Insurance liability	10,880	10,575
Health insurance [Member]
Schedule Of Accrued Liabilities [Line Items]
Insurance liability	$ 1,709	$ 1,350