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 9 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Non-cash stock compensation expense $ 11,631 $ 10,929 $ 39,803 $ 34,352
Restricted Stock Units to be Settled in Common Stock        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Shares granted (in shares) 0.2 0.2 1.5 1.4
Weighted average grant date fair value (in dollars per share) $ 33.73 $ 32.76 $ 34.43 $ 37.20
Awards vested (in shares) 0.0 0.0 1.4 1.5
Fair value of restricted stock, vested $ 1,500 $ 1,100 $ 47,700 $ 55,400
Non-cash stock compensation expense 10,400 $ 9,900 32,400 $ 31,200
Unrecognized compensation cost, related to unvested RSUs to be settled in common stock, total $ 51,900   $ 51,900  
Expected weighted average period to recognize compensation cost on RSUs to be settled in common stock     1 year 11 months 15 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