Net Income (Loss) per Share of Common Stock (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended			6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012		Jun. 30, 2013	Jun. 30, 2012
Numerators for earnings per share:
Net income (loss) that is available to common shareholders	$ 12,436	$ (10,143)		$ 14,425	$ (9,502)
Denominator for basic earnings per share:
Weighted average shares outstanding	21,288,897	20,837,843		21,202,411	20,803,629
Denominator for diluted earnings per share:
Effect of stock options and restricted stock units (1)	654,388	0	[1]	504,622	0	[1]
Adjusted weighted average shares and assumed conversions	21,943,285	20,837,843		21,707,033	20,803,629
Basic earnings (loss) per share	$ 0.58	$ (0.49)		$ 0.68	$ (0.46)
Diluted earnings (loss) per share	$ 0.57	$ (0.49)		$ 0.66	$ (0.46)
Anti-dilutive employee stock options and restricted stock units not included in the earnings per share calculation		437,680			424,483

[1] The effect of employee stock options and restricted stock units, 437,680 and 424,483 shares for the three months and six months ended June 30, 2012, respectively, were anti-dilutive and thus not included in the earnings per share calculation. This amount would have been dilutive if not for the net loss.