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Long-Term Debt - Additional information (Detail) - USD ($) |  | 3 Months Ended | 9 Months Ended |  |
--- | --- | --- | --- | --- | ---
Apr. 16, 2018 | Sep. 30, 2017 | Sep. 30, 2018 | Sep. 30, 2017 | Apr. 17, 2018 | Dec. 31, 2017
Debt Instrument [Line Items] |  |  |  |  |  |
Maximum consolidated debt reduction for unrestricted cash and cash equivalents for debt covenant calculation |  |  | $ 200,000,000 |  |  |
Additional interest expense |  | $ 369,000 | 458,000 | $ 1,089,000 |  |
Minimum [Member] |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Reduction of consolidated debt in the debt ratio calculation |  |  | $ 50,000,000 |  |  |
Including Acquisition Bridge Debt | Maximum |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Debt covenant |  |  | 350.00% |  |  |
Excluding Acquisition Bridge Debt | Maximum |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Debt covenant |  |  | 375.00% |  |  |
Revolving Facility |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Credit facility commitment |  |  | $ 700,000,000 |  |  |
Senior unsecured revolving facility, maturity period |  |  | 5 years |  |  |
Outstanding letters of credit |  | 1,963,000 | $ 2,301,000 | 1,963,000 |  | $ 2,301,000
Trade Receivable Facility |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Credit facility commitment |  |  |  |  | $ 400,000,000 |
Debt instrument maturity period |  |  | Sep. 25, 2019 |  |  |
Credit facility borrowing base |  | $ 402,754,000 | $ 465,217,000 | $ 402,754,000 |  | $ 338,784,000
Trade Receivable Facility | London Interbank Offered Rate(LIBOR) |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Basis spread on variable rate |  |  | 0.725% |  |  |
6.60% Senior Notes, Due 2018 |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Maturity date | Apr. 16, 2018 |  |  |  |  |
Repayments of credit facility | $ 300,000,000 |  |  |  |  |
Interest rate on notes | 6.60% |  | 6.60% |  |  |

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- Definition The amount by which consolidated debt, for purposes of calculating the debt covenant ratio, may be reduced for unrestricted cash and cash equivalents, provided no amounts are outstanding under the revolving credit facility and the AR credit facility. + References No definition available. + Details
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- Definition Maximum consolidated debt reduction for unrestricted cash and cash equivalents for debt covenant calculation. + References No definition available. + Details
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