Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands |
Mar. 31, 2018 |
Dec. 31, 2017 |
|---|---|---|
| Statement Of Financial Position [Abstract] | ||
| Accounts receivable, allowance for doubtful accounts | $ 8,934 | $ 8,405 |
| Common shares, par value | $ 0.10 | $ 0.10 |
| Common shares, authorized | 50,000,000 | 50,000,000 |
| Common shares, issued | 18,405,344 | 18,278,833 |
| Common shares, outstanding | 18,405,344 | 18,278,833 |