CONSOLIDATED STATEMENTS OF CHANGES IN COMMON STOCK EQUITY (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]
Balances at beginning of period at Dec. 31, 2008	$ 694,229	$ 64,733	$ 295,346	$ 643,322	$ (29,364)	$ (279,808)
Balances at beginning of period (in shares) at Dec. 31, 2008		64,732,652				19,848,900
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted common stock grants and deferred compensation (in shares)		114,703
Restricted common stock grants and deferred compensation	2,277	115	2,162
Performance share awards vested	0
Stock awards withheld for taxes	(165)	(8)	(157)
Stock awards withheld for taxes (in shares)		(8,249)
Forfeitures and lapsed restricted common stock (in shares)		(12,850)
Forfeitures and lapsed restricted common stock	(13)	(13)
Deferred taxes on stock incentive plan	328		328
Stock options exercised	3,768	267	3,501
Stock options exercised (in shares)		267,900
Net income	66,933			66,933
Other comprehensive income (loss)	(20,523)				(20,523)
Treasury stock acquired, at cost (in shares)						1,320,384
Treasury stock acquired, at cost	(24,105)					(24,105)
Balances at end of period at Dec. 31, 2009	722,729	65,094	301,180	710,255	(49,887)	(303,913)
Balances at end of period (in shares) at Dec. 31, 2009		65,094,156				21,169,284
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted common stock grants and deferred compensation (in shares)		112,891
Restricted common stock grants and deferred compensation	2,415	113	2,302
Performance share awards vested	663	10	653
Performance share awards vested (in shares)		9,525
Stock awards withheld for taxes	(247)	(11)	(236)
Stock awards withheld for taxes (in shares)		(10,261)
Forfeitures and lapsed restricted common stock (in shares)		(37,993)
Forfeitures and lapsed restricted common stock	(501)	(38)	(463)
Deferred taxes on stock incentive plan	350		350
Stock options exercised	1,379	97	1,282
Stock options exercised (in shares)		96,742
Net income	100,603			100,603
Other comprehensive income (loss)	16,710				16,710
Treasury stock acquired, at cost (in shares)						1,524,711
Treasury stock acquired, at cost	(33,726)					(33,726)
Balances at end of period at Dec. 31, 2010	810,375	65,265	305,068	810,858	(33,177)	(337,639)
Balances at end of period (in shares) at Dec. 31, 2010	65,121,689	65,265,060				22,693,995
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted common stock grants and deferred compensation (in shares)		118,110
Restricted common stock grants and deferred compensation	3,205	118	3,087
Performance share awards vested	628	41	587
Performance share awards vested (in shares)		40,895
Stock awards withheld for taxes	(739)	(24)	(715)
Stock awards withheld for taxes (in shares)		(23,702)
Forfeitures and lapsed restricted common stock (in shares)		(2,200)
Forfeitures and lapsed restricted common stock	(2)	(2)
Deferred taxes on stock incentive plan	1,112		1,112
Stock options exercised	692	54	638
Stock options exercised (in shares)		53,910
Net income	103,539			103,539
Other comprehensive income (loss)	(44,328)				(44,328)
Dividends declared	(27,223)			(27,223)
Treasury stock acquired, at cost (in shares)						2,798,924
Treasury stock acquired, at cost	(87,008)					(87,008)
Balances at end of period at Dec. 31, 2011	$ 760,251	$ 65,452	$ 309,777	$ 887,174	$ (77,505)	$ (424,647)
Balances at end of period (in shares) at Dec. 31, 2011	65,295,888	65,452,073				25,492,919