Quarterly report pursuant to Section 13 or 15(d)

Equity-Based Compensation (RSUs to be Settled in Cash) - Additional Information (Detail)

v3.7.0.1
Equity-Based Compensation (RSUs to be Settled in Cash) - Additional Information (Detail) - Restricted Stock Units to be Settled in Cash [Member] - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2017
Mar. 31, 2016
Dec. 31, 2016
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 $ 2.7 $ 1.5  
Payments to settle liabilities under compensation plan 2.4 $ 1.0  
Accrued liabilities under Compensation Plan $ 5.4   $ 5.1
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