Consolidated Statements Of Operations And Comprehensive Income (Parenthetical) (USD $) In Thousands | 3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2011 | Sep. 30, 2010 | Sep. 30, 2011 | Sep. 30, 2010 | |
| Consolidated Statements Of Operations And Comprehensive Income [Abstract] | ||||
| Prior service cost, tax | $ 28 | $ 13 | $ 84 | $ 38 |
| Actuarial loss, tax | $ 720 | $ 698 | $ 2,160 | $ 2,094 |