Net Income (Loss) per Share of Common Stock (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Numerators for earnings per share —
Net income (loss) that is available to common shareholders	$ 14,861	$ 7,127	$ 5,359	$ 21,532
Denominator for basic earnings per share —
Weighted average shares outstanding	20,896,291	20,181,558	20,834,742	20,079,412
Effect of stock options and restricted stock units	464,195	457,247	432,535	524,769
Effect of warrants	0	76,341	0	122,295
Total effect of dilutive securities	464,195	533,588	432,535	647,064
Denominator for diluted earnings per share —
Adjusted weighted average shares and assumed conversions	21,360,486	20,715,146	21,267,277	20,726,476
Basic earnings (loss) per share	$ 0.71	$ 0.35	$ 0.26	$ 1.07
Diluted earnings (loss) per share	$ 0.70	$ 0.34	$ 0.25	$ 1.04