Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Earnings Per Share [Abstract]
Distributed earnings allocated to common stock	$ 6,362	$ 6,073	$ 19,086	$ 18,220
Undistributed earnings allocated to common stock	4,125	5,673	21,040	19,809
Net earnings allocated to common shareholders	$ 10,487	$ 11,746	$ 40,126	$ 38,029
Average shares outstanding (in shares)	15,178,000	15,363,000	15,111,000	15,509,000
Effect of dilutive securities:
Warrant outstanding	0	62,000	37,000	62,000
Employee stock awards	20,000	20,000	21,000	23,000
Shares for diluted earnings per share (in shares)	15,198,000	15,445,000	15,169,000	15,594,000
Basic earnings per common share (in dollars per share)	$ 0.69	$ 0.76	$ 2.66	$ 2.45
Diluted earnings per share (in dollars per share)	$ 0.69	$ 0.76	$ 2.65	$ 2.44
Options to purchase shares of common stock, anti-dilutive (in shares)			0	13,953
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Lower Range Limit				$ 44.43