Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Earnings Per Share [Abstract]
Distributed earnings allocated to common stock	$ 6,375	$ 6,344	$ 12,751	$ 12,688
Undistributed earnings allocated to common stock	6,016	5,505	11,204	16,950
Net earnings allocated to common shareholders	$ 12,391	$ 11,849	$ 23,955	$ 29,638
Average shares outstanding (in shares)	14,889,000	15,104,000	14,903,000	15,079,000
Effect of dilutive securities:
Warrant outstanding	0	0	0	55,000
Employee stock awards	13,000	23,000	12,000	22,000
Shares for diluted earnings per share (in shares)	14,902,000	15,127,000	14,915,000	15,156,000
Basic earnings per common share (in dollars per share)	$ 0.83	$ 0.78	$ 1.61	$ 1.97
Diluted earnings per share (in dollars per share)	$ 0.83	$ 0.78	$ 1.61	$ 1.96
Options to purchase shares of common stock, anti-dilutive (in shares)			4,200	0