Property and Equipment, Net - Depreciation and Amortization Expense (Details) - USD ($) $ in Thousands |
3 Months Ended | |
|---|---|---|
Mar. 31, 2018 |
Mar. 31, 2017 |
|
| Depreciation and amortization expense | ||
| Depreciation and amortization expense related to property and equipment, including internal-use software | $ 1,514 | $ 1,267 |