Commitments and Contingencies - Summary of Rental Expense Incurred Under Leases (Detail) - USD ($) $ in Thousands |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Commitments and Contingencies Disclosure [Abstract] | |||
| Aircraft | $ 44,130 | $ 45,360 | $ 44,908 |
| Other | 9,451 | 8,358 | 7,790 |
| Total | $ 53,581 | $ 53,718 | $ 52,698 |