Long-Term Debt Long-Term Debt (Senior long-term debt) (Details) - USD ($) $ in Thousands |
Dec. 31, 2017 |
Dec. 31, 2016 |
|---|---|---|
| Debt Instrument [Line Items] | ||
| Accumulated Amortization, Debt Issuance Costs | $ 4,442 | $ 4,138 |
| Principal amount | 230,048 | |
| Debt Issuance Costs, Net | (967) | (1,270) |
| Less: current portion | (16,927) | (13,021) |
| Total long-term debt | 212,154 | 204,404 |
| Notes payable, other | Acquisition Debt | ||
| Debt Instrument [Line Items] | ||
| Principal amount | 10,548 | 12,245 |
| Revolving Credit Facility | Line of Credit | Revolving Credit Facility, Secured, Floating Rate | ||
| Debt Instrument [Line Items] | ||
| Principal amount | 92,000 | 67,700 |
| Credit Facility, Term Note | Notes payable, other | ||
| Debt Instrument [Line Items] | ||
| Principal amount | $ 127,500 | $ 138,750 |