Net Income per Share of Common Stock (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Numerator for earnings per share:
Net income that is available to common shareholders	$ 2,909	$ 16,719	$ 12,322	$ 34,225
Denominator for basic earnings per share:
Weighted average shares outstanding	21,894,017	21,796,172	21,869,922	21,816,323
Denominator for diluted earnings per share:
Effect of stock options and restricted stock units	177,176	402,536	156,304	452,161
Adjusted weighted average shares and assumed conversions	22,071,193	22,198,708	22,026,226	22,268,484
Basic earnings per share	$ 0.13	$ 0.77	$ 0.56	$ 1.57
Diluted earnings per share	$ 0.13	$ 0.75	$ 0.56	$ 1.54
Inclusion would have been anti-dilutive (excluded from calculation)
Shares excluded from diluted earnings per share due to:
Antidilutive securities excluded from diluted earnings per share	605,032	127,258	619,058	97,951