Earnings Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Numerator
Net income	$ 4,053	$ 7,482	$ 11,427	$ 20,665
Denominator for basic earnings per share:
Weighted average common shares outstanding	24,773	23,752	24,400	23,579
Dilutive potential common shares:
Weighted average common shares outstanding with assumed conversion	25,682	24,491	25,292	24,683
Basic earnings per share	$ 0.16	$ 0.32	$ 0.47	$ 0.88
Diluted earnings per share	$ 0.16	$ 0.31	$ 0.45	$ 0.84
Total number of anti-dilutive shares of stock options and nonvested stock excluded from calculation of diluted earnings per share	378	1,635	469	347
Stock options [Member]
Dilutive potential common shares:
Dilutive potential common shares	656	610	636	822
Restricted stock awards [Member]
Dilutive potential common shares:
Dilutive potential common shares	253	129	256	282