Earnings Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2014		Sep. 30, 2014		Jun. 30, 2014		Mar. 31, 2014		Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
BASIC
Net income	$ 8,902		$ 10,871		$ 8,488		$ 4,273		$ 5,553		$ 8,623		$ 5,841		$ 2,946		$ 32,534	$ 22,963	$ 16,553
Weighted-average common shares outstanding (in shares)	15,831		15,723		15,784		15,787		15,602		15,324		15,098		14,965		15,781	15,248	14,952
Basic earnings per share (in dollars per share)	$ 0.56	[1]	$ 0.69	[1]	$ 0.54	[1]	$ 0.27	[1]	$ 0.36	[1]	$ 0.56	[1]	$ 0.39	[1]	$ 0.20	[1]	$ 2.06	$ 1.51	$ 1.11
DILUTED
Net income	$ 8,902		$ 10,871		$ 8,488		$ 4,273		$ 5,553		$ 8,623		$ 5,841		$ 2,946		$ 32,534	$ 22,963	$ 16,553
Weighted-average common shares outstanding (in shares)	15,831		15,723		15,784		15,787		15,602		15,324		15,098		14,965		15,781	15,248	14,952
Dilutive effect of stock options and restricted stock (in shares)																	371	353	158
Weighted-average common shares outstanding on a diluted basis (in shares)	16,204		16,103		16,141		16,163		16,011		15,743		15,419		15,225		16,152	15,601	15,110
Diluted earnings per share (in dollars per share)	$ 0.55	[1]	$ 0.68	[1]	$ 0.53	[1]	$ 0.26	[1]	$ 0.35	[1]	$ 0.55	[1]	$ 0.38	[1]	$ 0.19	[1]	$ 2.01	$ 1.47	$ 1.10

[1] The earnings per common share calculations for each of the quarters were based upon the weighted average number of shares and share equivalents outstanding during each period, and the sum of the quarters may not be equal to the full year earnings per share amounts.