SEGMENT AND GEOGRAPHICAL INFORMATION - Long-lived Assets by Geographic Area (Details) - USD ($) $ in Thousands |
Sep. 30, 2019 |
Dec. 31, 2018 |
|---|---|---|
| Revenues from External Customers and Long-Lived Assets [Line Items] | ||
| Long-lived assets | $ 581,471 | $ 481,209 |
| United States | ||
| Revenues from External Customers and Long-Lived Assets [Line Items] | ||
| Long-lived assets | 570,273 | 471,970 |
| International | ||
| Revenues from External Customers and Long-Lived Assets [Line Items] | ||
| Long-lived assets | $ 11,198 | $ 9,239 |