Summary of Significant Accounting Policies, 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
Earnings Per Share [Abstract]
Stock options outstanding (in shares)	697				748				697	748	661
Antidilutive shares and options excluded from computation of earnings per share (in shares)									11	129	343
Net income	$ 8,649	$ 8,003	$ 8,615	$ 8,616	$ 6,676	$ 6,717	$ 7,842	$ 8,351	$ 33,883	$ 29,586	$ 16,303
Weighted average shares outstanding (in shares)									24,099	24,001	23,877
Basic income per share (in dollars per share)	$ 0.36	$ 0.33	$ 0.36	$ 0.36	$ 0.27	$ 0.28	$ 0.33	$ 0.35	$ 1.41	$ 1.23	$ 0.68
Effect of stock options outstanding [Abstract]
Assumed exercise, at the strike price at the beginning of year (in shares)									705	485	343
Assumed repurchase of shares under treasury stock method (in shares)									(444)	(371)	(201)
Diluted weighted average shares (in shares)									24,360	24,115	24,019
Diluted income per share (in dollars per share)	$ 0.35	$ 0.33	$ 0.35	$ 0.36					$ 1.39	$ 1.23	$ 0.68