Consolidated Statement of Changes in Shareholders' Equity (USD $) In Thousands	Total	Common stock [Member]	Additional paid-in capital	Retained earnings	Accumulated other comprehensive income	Treasury stock
Balance at Dec. 31, 2008	$ 2,640,023	$ 116,457	$ 881,534	$ 1,677,831	$ 27,536	$ (63,335)
Cumulative effect of accounting change (other-than-temporary impairments in investments)				4,301	(4,301)
Net earnings	353,868			353,868
Other comprehensive income (loss)	96,430				96,430
Issuance of 1,458, 1,404 and 1,040 shares for exercise of options, including tax effect, in 2011, 2010 and 2009, respectively.	19,198	993	18,205
Purchase of 12,645, 1,301, and 1,660 common shares in 2011, 2010 and 2009, respectively.	(35,464)					(35,464)
Issuance of 1,040 shares for debt conversion		1,040	(1,040)
Stock-based compensation	15,874	234	15,640
Cash dividends of $0.60, $0.56, $0.52 declared in 2011, 2010, and 2009, respectively.	(58,746)			(58,746)
Balance at Dec. 31, 2009	3,031,183	118,724	914,339	1,977,254	119,665	(98,799)
Net earnings	345,096			345,096
Other comprehensive income (loss)	(22,479)				(22,479)
Issuance of 1,458, 1,404 and 1,040 shares for exercise of options, including tax effect, in 2011, 2010 and 2009, respectively.	29,193	1,404	27,789
Purchase of 12,645, 1,301, and 1,660 common shares in 2011, 2010 and 2009, respectively.	(35,124)					(35,124)
Stock-based compensation	13,018	814	12,204
Cash dividends of $0.60, $0.56, $0.52 declared in 2011, 2010, and 2009, respectively.	(64,455)			(64,455)
Balance at Dec. 31, 2010	3,296,432	120,942	954,332	2,257,895	97,186	(133,923)
Net earnings	255,243			255,243
Other comprehensive income (loss)	130,473				130,473
Issuance of 1,458, 1,404 and 1,040 shares for exercise of options, including tax effect, in 2011, 2010 and 2009, respectively.	36,044	1,458	34,586
Purchase of 12,645, 1,301, and 1,660 common shares in 2011, 2010 and 2009, respectively.	(373,600)					(373,600)
Stock-based compensation	12,710	320	12,390
Cash dividends of $0.60, $0.56, $0.52 declared in 2011, 2010, and 2009, respectively.	(65,288)			(65,288)
Balance at Dec. 31, 2011	$ 3,292,014	$ 122,720	$ 1,001,308	$ 2,447,850	$ 227,659	$ (507,523)