CONSOLIDATED STATEMENTS OF STOCKHOLDERS' INVESTMENT (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended				12 Months Ended
	Dec. 31, 2011	Mar. 31, 2011	Dec. 31, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Beginning Balance		$ 1,204,068		$ 1,079,900	$ 1,204,068	$ 1,079,900	$ 1,107,221
Net income	109,214	97,028	103,161	84,012	431,612	387,026	360,830
Other comprehensive income -
Foreign currency translation adjustment					(2,690)	(4,774)	(3,819)
Unrealized gain (loss) on available-for-sale securities						(15)	18
Comprehensive income					428,922	382,237	357,029
Dividends declared, $1.20 in 2011,$1.04 in 2010 and $.97 in 2009 per share					(200,492)	(175,420)	(165,952)
Stock issued for employee benefit plans					9,596	17,733	17,741
Issuance of restricted stock					0	0	0
Stock-based compensation expense					38,060	37,583	20,801
Excess tax benefit on deferred compensation and employee stock plans					15,255	13,092	9,966
Repurchase of common stock					(246,935)	(151,057)	(266,906)
Ending Balance	1,248,474		1,204,068		1,248,474	1,204,068	1,079,900
Common Stock
Beginning Balance (in shares)		166,048,000		167,098,000	166,048,000	167,098,000	170,437,000
Beginning Balance		16,605		16,710	16,605	16,710	17,044
Other comprehensive income -
Stock issued for employee benefit plans (in shares)					673,000	1,065,000	1,189,000
Stock issued for employee benefit plans					67	106	119
Issuance of restricted stock (in shares)					244,000	376,000	558,000
Issuance of restricted stock					24	38	55
Stock-based compensation expense (in shares)					16,000	19,000	15,000
Stock-based compensation expense					2	2	2
Repurchase of common stock (in shares)					(3,540,000)	(2,510,000)	(5,101,000)
Repurchase of common stock					(354)	(251)	(510)
Ending Balance (in shares)	163,441,000		166,048,000		163,441,000	166,048,000	167,098,000
Ending Balance	16,344		16,605		16,344	16,605	16,710
Additional Paid-in Capital
Beginning Balance		178,087		165,104	178,087	165,104	177,486
Other comprehensive income -
Stock issued for employee benefit plans					(24,717)	(36,681)	(42,305)
Issuance of restricted stock					(24)	(38)	(55)
Stock-based compensation expense					37,193	36,610	20,012
Excess tax benefit on deferred compensation and employee stock plans					15,255	13,092	9,966
Ending Balance	205,794		178,087		205,794	178,087	165,104
Retained Earnings
Beginning Balance		1,613,912		1,402,306	1,613,912	1,402,306	1,207,428
Net income					431,612	387,026	360,830
Other comprehensive income -
Dividends declared, $1.20 in 2011,$1.04 in 2010 and $.97 in 2009 per share					(200,492)	(175,420)	(165,952)
Ending Balance	1,845,032		1,613,912		1,845,032	1,613,912	1,402,306
Accumulated Other Comprehensive Income (Loss)
Beginning Balance		(6,425)		(1,636)	(6,425)	(1,636)	2,165
Other comprehensive income -
Foreign currency translation adjustment					(2,690)	(4,774)	(3,819)
Unrealized gain (loss) on available-for-sale securities						(15)	18
Ending Balance	(9,115)		(6,425)		(9,115)	(6,425)	(1,636)
Treasury Stock
Beginning Balance		(598,111)		(502,584)	(598,111)	(502,584)	(296,902)
Other comprehensive income -
Stock issued for employee benefit plans					34,246	54,308	59,927
Stock-based compensation expense					865	971	787
Repurchase of common stock					(246,581)	(150,806)	(266,396)
Ending Balance	$ (809,581)		$ (598,111)		$ (809,581)	$ (598,111)	$ (502,584)