Significant Accounting Policies - Recent Accounting Pronouncements (Details) - USD ($) $ in Thousands |
Dec. 31, 2016 |
Dec. 31, 2015 |
|---|---|---|
| Recent Accounting Pronouncements | ||
| Other assets | $ 6,050 | $ 8,039 |
| Long-term debt | $ 724,009 | 837,654 |
| Accounting Standards Update 2015-03 | ||
| Recent Accounting Pronouncements | ||
| Other assets | 10,300 | |
| Long-term debt | $ 10,300 |