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Equity-Based Compensation (RSUs to be Settled in Cash) - Additional Information (Detail) - Restricted Stock Units to be Settled in Cash [Member] - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Number of common stock shares that may be received by RSU holder 1    
Compensation expense related to Restricted Stock Units to be settled in cash $ 7.0 $ 4.0 $ 3.9
Payments to settle liabilities under compensation plan 4.6 4.2 $ 3.1
Accrued liabilities under Compensation Plan $ 5.1 $ 2.7  
Minimum [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vesting period for restricted stock and restricted stock units 2 years    
Maximum [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vesting period for restricted stock and restricted stock units 3 years