CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands |
Sep. 30, 2015 |
Dec. 31, 2014 |
|---|---|---|
| Statement Of Financial Position [Abstract] | ||
| Accounts receivable, allowance for doubtful accounts | $ 18,079 | $ 19,725 |
| Common stock, par value | $ 0.10 | $ 0.10 |
| Common stock, authorized | 100,000,000 | 100,000,000 |
| Common stock, issued | 74,435,628 | 74,435,628 |
| Treasury stock, shares | 36,874,672 | 35,719,041 |