Consolidated Statements of Shareholders' Equity (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock	Paid-in Capital	Accumulated Other Comprehensive Earnings (Loss)	Retained Earnings	Deferred Compensation	Treasury Stock at Cost
Balance at Dec. 31, 2010	$ 769,151	$ 64,635	$ 182,749	$ 95,992	$ 812,150	$ 6,474	$ (392,849)
Balance (in shares) at Dec. 31, 2010		41,929,080
Increase (Decrease) in Shareholders' Equity
Net earnings	126,598				126,598
Other comprehensive earnings, net of tax	21,333			21,333
Treasury shares purchased	(6,624)						(6,624)
Treasury shares purchased (in shares)		(223,912)
Deferred compensation under Rabbi trust plans						3,971	(3,971)
Stock option excess tax benefit	4,210		4,210
Exercise of stock options	8,821	619	8,202
Exercise of stock options (in shares)		619,106
Dividends declared ($2.17, $3.13 and $3.10 per share during 2013, 2012 and 2011, respectively)	(130,855)				(130,855)
Balance at Dec. 31, 2011	792,634	65,254	195,161	117,325	807,893	10,445	(403,444)
Balance (in shares) at Dec. 31, 2011		42,324,274
Increase (Decrease) in Shareholders' Equity
Net earnings	103,346				103,346
Other comprehensive earnings, net of tax	25,845			25,845
Deferred compensation under Rabbi trust plans						661	(661)
Stock option excess tax benefit	1,471		1,471
Exercise of stock options	6,104	201	5,903
Exercise of stock options (in shares)		200,974
Dividends declared ($2.17, $3.13 and $3.10 per share during 2013, 2012 and 2011, respectively)	(133,037)				(133,037)
Balance at Dec. 31, 2012	796,363	65,455	202,535	143,170	778,202	11,106	(404,105)
Balance (in shares) at Dec. 31, 2012		42,525,248
Increase (Decrease) in Shareholders' Equity
Net earnings	126,255				126,255
Other comprehensive earnings, net of tax	(7,143)			(7,143)
Deferred compensation under Rabbi trust plans						456	(456)
Stock option excess tax benefit	6,310		6,310
Exercise of stock options	318	458	(140)
Exercise of stock options (in shares)		457,176
Dividends declared ($2.17, $3.13 and $3.10 per share during 2013, 2012 and 2011, respectively)	(93,137)				(93,137)
Balance at Dec. 31, 2013	$ 828,966	$ 65,913	$ 208,705	$ 136,027	$ 811,320	$ 11,562	$ (404,561)
Balance (in shares) at Dec. 31, 2013		42,982,424