Stock Based Compensation - Summary of Expense Related to Share-Based Payments (Detail) - USD ($) $ in Thousands |
3 Months Ended | 12 Months Ended | ||
|---|---|---|---|---|
Dec. 31, 2016 |
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
|
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||
| Stock-based compensation | $ 31,800 | $ 93,297 | $ 63,946 | $ 90,122 |
| General and Administrative Expense | ||||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||
| Stock-based compensation | 93,297 | 63,946 | 90,122 | |
| General and Administrative Expense | Stock options | ||||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||
| Stock-based compensation | 56,400 | 35,234 | 44,260 | |
| General and Administrative Expense | Restricted stock | ||||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||
| Stock-based compensation | $ 36,897 | $ 28,712 | $ 45,862 | |