Significant Accounting Policies - Restricted Invested Assets (Details) - USD ($) $ in Thousands |
Dec. 31, 2016 |
Dec. 31, 2015 |
|---|---|---|
| Restricted Cash and Cash Equivalents Items [Line Items] | ||
| Restricted invested assets | $ 315 | $ 316 |
| Chesterfield, Missouri facility | ||
| Restricted Cash and Cash Equivalents Items [Line Items] | ||
| Restricted invested assets | $ 315 | $ 316 |