Consolidated Statements of Changes in Shareholders’ Equity (USD $) In Thousands	Common Stock [Member]	Accumulated Deferred Compensation [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]	Total
Balance at Dec. 31, 2010	$ 378,885	$ 2,724	$ 159	$ 163,519	$ 545,287
Balance (in Shares) at Dec. 31, 2010	29,090
Net income for the year				87,888	87,888
Other comprehensive (loss) income, net of tax			11,210		11,210
Exercise of stock options	14,374				14,374
Exercise of stock options (in Shares)	360
Tax benefits increase (decrease) upon exercise of stock option	(248)				(248)
Restricted stock activity	455	336			791
Restricted stock activity (in Shares)	15
Stock based compensation	1,425				1,425
Stock awarded to employees	89				89
Stock awarded to employees (in Shares)	2
Purchase and retirement of stock	(17,205)			(43,300)	(60,505)
Purchase and retirement of stock (in Shares)	(1,317)
Dividends				(41,670)	(41,670)
Balance at Dec. 31, 2011	377,775	3,060	11,369	166,437	558,641
Balance (in Shares) at Dec. 31, 2011	28,150
Net income for the year				81,127	81,127
Other comprehensive (loss) income, net of tax			3,256		3,256
Exercise of stock options	7,635				7,635
Exercise of stock options (in Shares)	185
Tax benefits increase (decrease) upon exercise of stock option	(119)				(119)
Restricted stock activity	482	41			523
Restricted stock activity (in Shares)	11
Stock based compensation	1,450				1,450
Stock awarded to employees	93				93
Stock awarded to employees (in Shares)	2
Purchase and retirement of stock	(15,304)			(36,195)	(51,499)
Purchase and retirement of stock (in Shares)	(1,135)
Dividends				(41,005)	(41,005)
Balance at Dec. 31, 2012	372,012	3,101	14,625	170,364	560,102
Balance (in Shares) at Dec. 31, 2012	27,213
Net income for the year				67,177	67,177
Other comprehensive (loss) income, net of tax			(10,312)		(10,312)
Exercise of stock options	21,499				21,499
Exercise of stock options (in Shares)	479				478
Tax benefits increase (decrease) upon exercise of stock option	(298)				(298)
Restricted stock activity	1,068	(390)			678
Restricted stock activity (in Shares)	15
Stock based compensation	1,397				1,397
Stock awarded to employees	107				107
Stock awarded to employees (in Shares)	2
Purchase and retirement of stock	(16,839)			(40,481)	(57,320)
Purchase and retirement of stock (in Shares)	(1,199)
Dividends				(40,096)	(40,096)
Balance at Dec. 31, 2013	$ 378,946	$ 2,711	$ 4,313	$ 156,964	$ 542,934
Balance (in Shares) at Dec. 31, 2013	26,510