Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands |
Jun. 30, 2019 |
Dec. 31, 2018 |
|---|---|---|
| Current assets: | ||
| Allowance for doubtful accounts | $ 3,981 | $ 4,618 |
| Noncurrent assets: | ||
| Property and equipment, accumulated depreciation | 123,054 | 110,010 |
| Customer relationships and other intangible assets, accumulated amortization | $ 76,053 | $ 69,855 |
| 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) | 31,498,159 | 31,345,220 |
| Common stock, shares outstanding (in shares) | 26,396,576 | 27,397,760 |
| Treasury stock, shares (in shares) | 5,101,583 | 3,947,460 |