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Long-Term Debt - Additional information (Detail) - USD ($)
3 Months Ended 6 Months Ended
Apr. 16, 2018
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 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   $ 111,000 $ 364,000 458,000 $ 720,000    
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   3.50   3.50      
Excluding Acquisition Bridge Debt | Maximum              
Debt Instrument [Line Items]              
Debt covenant   3.75   3.75      
Revolving Facility              
Debt Instrument [Line Items]              
Credit facility commitment   $ 700,000,000   $ 700,000,000      
Senior unsecured revolving facility, maturity period       5 years      
Outstanding letters of credit   2,301,000 2,507,000 $ 2,301,000 2,507,000   $ 2,301,000
Trade Receivable Facility              
Debt Instrument [Line Items]              
Credit facility commitment           $ 400,000,000  
Debt instrument maturity period       Sep. 26, 2018      
Credit facility borrowing base   $ 490,362,000 $ 422,624,000 $ 490,362,000 $ 422,624,000   $ 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%   6.60%