Property and equipment - Summary by type (Details) - USD ($) $ in Thousands |
Jun. 30, 2018 |
Dec. 31, 2017 |
|---|---|---|
| Property and equipment | ||
| Total property and equipment | $ 534,703 | $ 502,646 |
| Less: accumulated depreciation and amortization | (256,419) | (240,287) |
| Total property and equipment, net | 278,284 | 262,359 |
| Leasehold improvements | ||
| Property and equipment | ||
| Total property and equipment | 434,112 | 418,023 |
| Software | ||
| Property and equipment | ||
| Total property and equipment | 46,389 | 42,281 |
| Construction in progress | ||
| Property and equipment | ||
| Total property and equipment | 39,055 | 27,291 |
| Computer equipment | ||
| Property and equipment | ||
| Total property and equipment | 13,378 | 13,245 |
| Furniture, fixtures and office equipment | ||
| Property and equipment | ||
| Total property and equipment | $ 1,769 | $ 1,806 |