Earnings Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
BASIC
Net income	$ 8,623	$ 6,850	$ 17,410	$ 13,635
Weighted-average common shares outstanding (in shares)	15,324	14,984	15,129	14,931
Basic earnings per share (in dollars per share)	$ 0.56	$ 0.46	$ 1.15	$ 0.91
DILUTED
Net income	$ 8,623	$ 6,850	$ 17,410	$ 13,635
Weighted-average common shares outstanding (in shares)	15,324	14,984	15,129	14,931
Dilutive effect of stock options and restricted stock (in shares)	419	115	333	156
Weighted-average common shares outstanding on a diluted basis (in shares)	15,743	15,099	15,462	15,087
Diluted earnings per share (in dollars per share)	$ 0.55	$ 0.45	$ 1.13	$ 0.90