Quarterly report pursuant to Section 13 or 15(d)

Equity-Based Compensation - RSUs to be Settled in Common Stock (Detail)

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Equity-Based Compensation - RSUs to be Settled in Common Stock (Detail) - USD ($)
$ / shares in Units, $ in Thousands, shares in Millions
3 Months Ended 6 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Non-cash stock compensation expense $ 13,485 $ 11,557 $ 28,172 $ 23,423
Restricted Stock Units to be Settled in Common Stock        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Granted, shares (in shares)   0.1 1.3 1.2
Granted, weighted average grant date fair value, per share (in usd per share) $ 36.38 $ 33.32 $ 34.52 $ 37.76
Awards vested (in shares) 0.1 0.1 1.3 1.4
Fair value of restricted stock, vested $ 3,800 $ 3,800 $ 46,200 $ 54,300
Non-cash stock compensation expense 10,800 $ 10,100 22,000 $ 21,300
Unrecognized compensation cost, related to unvested RSUs to be settled in common stock, total $ 56,200   $ 56,200  
Expected weighted average period to recognize compensation cost on RSUs to be settled in common stock (in years)     2 years 10 days  
Share-based Compensation Award, Tranche One | Restricted Stock Units to be Settled in Common Stock        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Vesting period for RSUs to be settled in stock     2 years  
Share-based Compensation Award, Tranche Two | Restricted Stock Units to be Settled in Common Stock        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Vesting period for RSUs to be settled in stock     3 years  
Share-based Compensation Award, Tranche Three | Restricted Stock Units to be Settled in Common Stock        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Vesting period for RSUs to be settled in stock     5 years