Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands |
Jun. 30, 2018 |
Dec. 31, 2017 |
|---|---|---|
| Current assets: | ||
| Allowance for doubtful accounts | $ 5,344 | $ 3,745 |
| Noncurrent assets: | ||
| Property and equipment, accumulated depreciation | 97,857 | 86,549 |
| Customer relationships and other intangible assets, accumulated amortization | $ 63,309 | $ 56,834 |
| Stockholders' equity: | ||
| Common stock, par value (in usd per share) | $ 0.0001 | $ 0.0001 |
| Common stock, shares authorized (in shares) | 100,000,000 | 100,000,000 |
| Common stock, shares issued (in shares) | 31,243,465 | 30,768,050 |
| Common stock, shares outstanding (in shares) | 27,716,595 | 27,241,180 |
| Treasury stock, shares (in shares) | 3,526,870 | 3,526,870 |