Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Earnings Per Share [Abstract]
Distributed earnings allocated to common stock	$ 6,344	$ 6,178	$ 12,688	$ 12,356
Undistributed earnings allocated to common stock	5,505	6,448	16,950	13,931
Net earnings allocated to common shareholders	$ 11,849	$ 12,626	$ 29,638	$ 26,287
Average shares outstanding (in shares)	15,104,000	15,556,000	15,079,000	15,583,000
Effect of dilutive securities:
Warrant outstanding	0	62,000	0	62,000
Employee stock awards	23,000	88,000	22,000	93,000
Shares for diluted earnings per share (in shares)	15,127,000	15,706,000	15,101,000	15,738,000
Basic earnings per share (in dollars per share)	$ 0.78	$ 0.81	$ 1.97	$ 1.69
Diluted earnings per share (in dollars per share)	$ 0.78	$ 0.80	$ 1.96	$ 1.67
Options to purchase shares of common stock, anti-dilutive (in shares)			0	0