Stock-Based Compensation - Summary of Employee and Director Restricted Stock and Restricted Stock Highlights (Detail) - Employee Restricted Stock Units and Director Restricted Stock Units - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | ||
---|---|---|---|---|
Jun. 30, 2019 |
Jun. 30, 2018 |
Jun. 30, 2019 |
Jun. 30, 2018 |
|
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||
Fair value of vested restricted stock units | $ 3.5 | $ 5.6 | $ 18.7 | $ 9.9 |
Tax benefit recognized from vested restricted stock units | $ 0.8 | $ 1.1 | $ 3.4 | $ 2.1 |