Consolidated Statements of Comprehensive Income (USD $) In Thousands | 3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2011 | Sep. 30, 2010 | Sep. 30, 2011 | Sep. 30, 2010 | |
| Net income | $ 25,266 | $ 16,176 | $ 65,102 | $ 48,113 |
| Unrealized gain on short-term investments (net of income tax expense of $1 for the nine months ended September 30, 2010) | 0 | 0 | 0 | 1 |
| Comprehensive income | $ 25,266 | $ 16,176 | $ 65,102 | $ 48,114 |