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Long-Term Cash Incentive Plan - Additional Information (Detail) - USD ($)
$ in Millions
 12 Months Ended
Feb. 12, 2016
Dec. 31, 2017
Dec. 31, 2016
Long Term Incentive Plan 2016      
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]      
Estimated payment of plan including employer cost   $ 4.7  
Deferred Compensation Cash-based Arrangements, Liability, Current and Noncurrent   $ 1.3 $ 1.9
Long Term Incentive Plan 2013      
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]      
Estimated payment of plan including employer cost $ 4.8    
Deferred Compensation Cash-based Arrangements, Liability, Current and Noncurrent     $ 4.8