Property and Equipment - Additional Information (Details) - USD ($) $ in Thousands |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
|
| Property Plant And Equipment [Line Items] | |||
| Depreciation, depletion and amortization, nonproduction | $ 105,891 | $ 63,449 | $ 56,921 |
| Depreciation expense including amortization expense on capital leases | 58,900 | $ 51,000 | |
| Assets Acquired Under Capital Lease | |||
| Property Plant And Equipment [Line Items] | |||
| Accumulated, depreciation and amortization | 400 | $ 2,900 | |
| Capital Leases | |||
| Property Plant And Equipment [Line Items] | |||
| Depreciation, depletion and amortization, nonproduction | $ 100,900 | ||