Fair Value Measurement - Recurring Basis (Details) - Contingent consideration for acquisitions - USD ($) $ in Thousands |
12 Months Ended | |
|---|---|---|
Dec. 31, 2016 |
Dec. 31, 2015 |
|
| Liabilities measured at fair value on a recurring basis | ||
| Balance at beginning of period | $ 41,712 | $ 39,319 |
| Fair value of contingent consideration at measurement date | 4,500 | 5,000 |
| Change in estimates included in earnings | 7,904 | (359) |
| Settlements | (7,548) | (2,248) |
| Balance at end of period | $ 46,568 | $ 41,712 |