Summary of Significant Accounting Policies - Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands |
Mar. 31, 2018 |
Dec. 31, 2017 |
Mar. 31, 2017 |
|---|---|---|---|
| Accumulated Other Comprehensive Income (Loss) [Line Items] | |||
| Accumulated other comprehensive loss | $ (5,554) | $ (7,328) | $ (12,544) |
| AOCI Attributable to Parent | |||
| Accumulated Other Comprehensive Income (Loss) [Line Items] | |||
| Accumulated other comprehensive loss | (5,554) | (7,328) | (12,544) |
| Foreign currency translation adjustments | |||
| Accumulated Other Comprehensive Income (Loss) [Line Items] | |||
| Accumulated other comprehensive loss | (6,528) | (7,478) | (11,776) |
| Unrealized gains (losses) on interest rate swaps, net of tax | |||
| Accumulated Other Comprehensive Income (Loss) [Line Items] | |||
| Accumulated other comprehensive loss | $ 974 | $ 150 | $ (768) |