Consolidated Statements of Stockholders' Equity (Unaudited) (USD $) In Thousands, except Share data	Total USD ($)	Common Stock Outstanding	Common Stock USD ($)	Value of Shares Held in Rabbi Trust at Cost USD ($)	Deferred Compensation Obligation USD ($)	Additional Paid in Capital USD ($)	Retained Earnings USD ($)	Accumulated Other Comprehensive Loss USD ($)
Balance at December 31, 2013 at Dec. 31, 2012	$ 529,320		$ 225	$ (3,179)	$ 3,179	$ 269,950	$ 263,671	$ (4,526)
Balance at December 31, 2013 at Dec. 31, 2012		22,774,009
Net income	39,665						39,665
Other comprehensive income	(2,534)							(2,534)
Common dividend declared ($0.72 per share)	(15,128)						(15,128)
Proceeds from exercise of stock options		76,253
Proceeds from exercise of stock options	1,994		1			1,993
Tax benefit related to equity award activity	412					412
Equity based compensation	1,923					1,923
Restricted stock awards issued, net of awards surrendered		89,431
Restricted stock awards issued, net of awards surrendered	(669)		1			(670)
Stock Issued During Period, Shares, Other		19,594
Stock Issued During Period, Value, Other	656					656
Increase (Decrease) in Deferred Compensation				(165)	165
Deferred Compensation Obligation Value
Tax benefit related to deferred compensation distributions	105					105
Balance at September 30, 2014 at Sep. 30, 2013	555,744		227	(3,344)	3,344	274,369	288,208	(7,060)
Balance at September 30, 2014 at Sep. 30, 2013		22,959,287
Balance at December 31, 2013 at Dec. 31, 2013	591,540		235	(3,404)	3,404	305,179	293,560	(7,434)
Balance at December 31, 2013 at Dec. 31, 2013	23,805,984	23,805,984
Net income	43,867						43,867
Other comprehensive income	5,430							5,430
Common dividend declared ($0.72 per share)	(17,201)						(17,201)
Proceeds from exercise of stock options		24,609
Proceeds from exercise of stock options	583		1			582
Tax benefit related to equity award activity	438					438
Equity based compensation	2,075					2,075
Restricted stock awards issued, net of awards surrendered		55,675
Restricted stock awards issued, net of awards surrendered	(643)		1			(644)
Stock Issued During Period, Shares, Other		25,410
Stock Issued During Period, Value, Other	959					959
Increase (Decrease) in Deferred Compensation				(187)	187
Tax benefit related to deferred compensation distributions	134					134
Balance at September 30, 2014 at Sep. 30, 2014	$ 627,182		$ 237	$ (3,591)	$ 3,591	$ 308,723	$ 320,226	$ (2,004)
Balance at September 30, 2014 at Sep. 30, 2014	23,911,678	23,911,678