CONSOLIDATED STATEMENTS OF STOCKHOLDERS EQUITY (USD $) In Thousands, except Share data	Total	COMMON STOCK [Member]	CAPITAL SURPLUS [Member]	RETAINED EARNINGS [Member]	ACCUMULATED OTHER COMPREHENSIVE INCOME [Member]
Balance at beginning of period at Dec. 31, 2010		$ 15,369	$ 73,040	$ 361,680	$ 8,505
Issued at beginning of period, Shares at Dec. 31, 2010		15,368,717
Net income	45,621			45,621
Net change	939				939
Common stock issued		51	990
Dividends on common stock ($1.20, $1.12 and $1.04 per share, respectively)				(15,787)
Shares issued, Shares		50,862
Tax effect of stock options			357
Stock-based compensation arrangements			3,075
Common stock acquired and canceled		(302)		(10,497)
Shares acquired and canceled, Shares		(302,149)
Balance at end of period at Dec. 31, 2011	483,041	15,118	77,462	381,017	9,444
Issued at end of period, Shares at Dec. 31, 2011		15,117,430
Net income	51,900			51,900
Net change	(3,127)				(3,127)
Common stock issued		131	2,139
Dividends on common stock ($1.20, $1.12 and $1.04 per share, respectively)				(17,061)
Shares issued, Shares		131,665
Tax effect of stock options			1,270
Stock-based compensation arrangements			1,530
Common stock acquired and canceled		(7)		(249)
Shares acquired and canceled, Shares		(6,787)
Balance at end of period at Dec. 31, 2012	519,567	15,242	82,401	415,607	6,317
Issued at end of period, Shares at Dec. 31, 2012		15,242,308
Net income	54,317			54,317
Net change	(2,410)				(2,410)
Common stock issued		158	3,590
Dividends on common stock ($1.20, $1.12 and $1.04 per share, respectively)				(18,327)
Shares issued, Shares		157,155
Tax effect of stock options			1,452
Stock-based compensation arrangements			1,360
Common stock acquired and canceled		(66)		(2,644)
Shares acquired and canceled, Shares		(65,841)
Balance at end of period at Dec. 31, 2013	$ 556,997	$ 15,334	$ 88,803	$ 448,953	$ 3,907
Issued at end of period, Shares at Dec. 31, 2013		15,333,622