CONSOLIDATED STATEMENTS OF STOCKHOLDERS' INVESTMENT (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended				12 Months Ended
	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance		$ 939,724		$ 1,504,372	$ 939,724	$ 1,504,372	$ 1,248,474
Net income	112,947	93,187	92,952	103,343	449,711	415,904	593,804
Foreign currency translation adjustment					(17,990)	(1,275)	(230)
Comprehensive income					431,721	414,629	593,574
Dividends declared, $1.43 in 2014, $1.40 in 2013 and $1.34 in 2012 per share					(215,005)	(220,300)	(220,607)
Stock issued for acquisition							60,152
Stock issued for employee benefit plans					(667)	(34,978)	8,086
Issuance of restricted stock						0	0
Stock-based compensation expense					47,721	9,096	59,463
Excess tax benefit on deferred compensation and employee stock plans					7,558	27,209	12,294
Repurchase of common stock					(164,037)	(760,304)	(257,064)
Ending Balance	1,047,015		939,724		1,047,015	939,724	1,504,372
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance (in shares)		150,197,000		161,327,000	150,197,000	161,327,000	163,441,000
Beginning Balance		15,020		16,133	15,020	16,133	16,344
Stock issued for acquisition (in shares)							1,108,000
Stock issued for acquisition							111
Stock issued for employee benefit plans (in shares)					405,000	263,000	712,000
Stock issued for employee benefit plans					40	26	71
Issuance of restricted stock (in shares)					410,000	335,000	276,000
Issuance of restricted stock					(41)	34	28
Stock-based compensation expense (in shares)					30,000	30,000	28,000
Stock-based compensation expense					3	3	3
Repurchase of common stock (in shares)					(3,764,000)	(11,758,000)	(4,238,000)
Repurchase of common stock					(376)	(1,176)	(424)
Ending Balance	14,646		15,020		14,646	15,020	16,133
Ending Balance (in shares)	146,458,000		150,197,000		146,458,000	150,197,000	161,327,000
Additional Paid-in Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance		217,894		303,479	217,894	303,479	205,794
Stock issued for acquisition							60,041
Stock issued for employee benefit plans					(24,644)	(45,106)	(32,435)
Issuance of restricted stock					41	(34)	(28)
Stock-based compensation expense					46,119	7,346	57,813
Excess tax benefit on deferred compensation and employee stock plans					7,558	27,209	12,294
Repurchase of common stock					75,000	(75,000)
Ending Balance	321,968		217,894		321,968	217,894	303,479
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance		2,413,833		2,218,229	2,413,833	2,218,229	1,845,032
Net income					449,711	415,904	593,804
Dividends declared, $1.43 in 2014, $1.40 in 2013 and $1.34 in 2012 per share					(215,005)	(220,300)	(220,607)
Ending Balance	2,648,539		2,413,833		2,648,539	2,413,833	2,218,229
Accumulated Other Comprehensive Loss
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance		(10,620)		(9,345)	(10,620)	(9,345)	(9,115)
Foreign currency translation adjustment					(17,990)	(1,275)	(230)
Ending Balance	(28,610)		(10,620)		(28,610)	(10,620)	(9,345)
Treasury Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance		(1,696,403)		(1,024,124)	(1,696,403)	(1,024,124)	(809,581)
Stock issued for employee benefit plans					23,937	10,102	40,450
Stock-based compensation expense					1,599	1,747	1,647
Repurchase of common stock					(238,661)	(684,128)	(256,640)
Ending Balance	$ (1,909,528)		$ (1,696,403)		$ (1,909,528)	$ (1,696,403)	$ (1,024,124)