Consolidated Statements of Shareholders' Equity (USD $) In Thousands	Total	Common Stock	Restricted Stock	Additional Paid-In Capital	Retained Earnings	Accumulated other Comprehensive Income(Loss)
Beginning Balance at Dec. 31, 2009	$ 350,038	$ 1	$ 9,042	$ 66,319	$ 288,754	$ (14,078)
Beginning Balance (in shares) at Dec. 31, 2009		41,381	158
Net income	113,593				113,593
Other comprehensive income, net of tax	15,493					15,493
Excess tax benefits on stock-based compensation plans, share		69
Excess tax benefits on stock-based compensation plans	1,101			1,101
Restricted stock activity (in shares)		48	86
Restricted stock activity	1,966		1,966
Dividends	(30,721)				(30,721)
Ending Balance at Dec. 31, 2010	451,470	1	11,008	67,420	371,626	1,415
Ending Balance (in shares) at Dec. 31, 2010		41,498	244
Net income	122,856				122,856
Other comprehensive income, net of tax	(73,849)					(73,849)
Excess tax benefits on stock-based compensation plans, share		1
Excess tax benefits on stock-based compensation plans	2			2
Restricted stock activity (in shares)		72	(1)
Restricted stock activity	2,684		2,684
Dividends	(9,974)				(9,974)
Ending Balance at Dec. 31, 2011	493,189	1	13,692	67,422	484,508	(72,434)
Ending Balance (in shares) at Dec. 31, 2011		41,571	243
Net income	185,543				185,543
Other comprehensive income, net of tax	(13,699)					(13,699)
Excess tax benefits on stock-based compensation plans	645		645
Restricted stock activity (in shares)		89	18
Restricted stock activity	3,725		3,725
Dividends	(103,733)				(103,733)
Ending Balance at Dec. 31, 2012	$ 565,670	$ 1	$ 18,062	$ 67,422	$ 566,318	$ (86,133)
Ending Balance (in shares) at Dec. 31, 2012		41,660	261