Consolidated Statements of Stockholders' Investment - USD ($) shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018	Jan. 01, 2018
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	$ 1,659,311	$ 1,652,561	$ 1,595,087	$ 1,518,159	$ 1,484,672	$ 1,425,745	$ 1,595,087	$ 1,425,745
Net income	146,894	169,180	161,788	175,895	159,163	142,297	477,862	477,355
Cumulative effect change - revenue recognition									$ 9,239
Foreign currency translation	(18,576)	(5,688)	5,297	(10,877)	(27,512)	(565)
Dividends declared	(68,855)	(69,268)	(69,683)	(64,716)	(65,084)	(65,384)
Stock issued for employee benefit plans	10,818	7,699	7,573	8,868	10,547	6,406
Issuance of restricted stock, net of forfeitures	0	0	0	0	0	0
Stock-based compensation expense	8,850	14,684	17,123	23,771	26,570	18,134
Repurchase of common stock	(65,346)	(109,857)	(64,624)	(84,497)	(70,197)	(51,200)
Ending balance	$ 1,673,096	$ 1,659,311	$ 1,652,561	$ 1,566,603	$ 1,518,159	$ 1,484,672	$ 1,673,096	$ 1,566,603
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance (in shares)	135,731	136,889	137,284	138,744	139,353	139,542	137,284	139,542
Beginning balance	$ 13,573	$ 13,689	$ 13,728	$ 13,874	$ 13,935	$ 13,954	$ 13,728	$ 13,954
Stock issued for employee benefit plans (in shares)	194	129	342	144	174	370
Stock issued for employee benefit plans	$ 20	$ 13	$ 34	$ 15	$ 17	$ 37
Issuance of restricted stock, net of forfeitures (in shares)			(3)			(2)
Issuance of restricted stock, net of forfeitures (in shares)	9	23		2	1
Issuance of restricted stock, net of forfeitures	$ 1	$ 2	$ 0	$ 0	$ 0	$ 0
Stock-based compensation expense (in shares)	0	0	0	0	0	0
Stock-based compensation expense	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0
Repurchase of common stock (in shares)	(782)	(1,310)	(734)	(890)	(784)	(557)
Repurchase of common stock	$ (79)	$ (131)	$ (73)	$ (89)	$ (78)	$ (56)
Ending balance (in shares)	135,152	135,731	136,889	138,000	138,744	139,353	135,152	138,000
Ending balance	$ 13,515	$ 13,573	$ 13,689	$ 13,800	$ 13,874	$ 13,935	$ 13,515	$ 13,800
Additional Paid-in Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	541,090	527,089	521,486	478,451	451,966	444,280	521,486	444,280
Stock issued for employee benefit plans	(561)	(681)	(11,520)	217	(85)	(10,441)
Issuance of restricted stock, net of forfeitures	(1)	(2)	0	0	0	0
Stock-based compensation expense	8,850	14,684	17,123	23,771	26,570	18,127
Ending balance	549,378	541,090	527,089	502,439	478,451	451,966	549,378	502,439
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	4,037,610	3,937,698	3,845,593	3,617,324	3,523,245	3,437,093	3,845,593	3,437,093
Net income	146,894	169,180	161,788	175,895	159,163	142,297
Cumulative effect change - revenue recognition									$ 9,239
Dividends declared	(68,855)	(69,268)	(69,683)	(64,716)	(65,084)	(65,384)
Ending balance	4,115,649	4,037,610	3,937,698	3,728,503	3,617,324	3,523,245	4,115,649	3,728,503
Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(72,326)	(66,638)	(71,935)	(46,537)	(19,025)	(18,460)	(71,935)	(18,460)
Foreign currency translation	(18,576)	(5,688)	5,297	(10,877)	(27,512)	(565)
Ending balance	(90,902)	(72,326)	(66,638)	(57,414)	(46,537)	(19,025)	(90,902)	(57,414)
Treasury Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(2,860,636)	(2,759,277)	(2,713,785)	(2,544,953)	(2,485,449)	(2,451,122)	(2,713,785)	(2,451,122)
Stock issued for employee benefit plans	11,359	8,367	19,059	8,636	10,615	16,810
Stock-based compensation expense	0	0	0	0	0	7
Repurchase of common stock	(65,267)	(109,726)	(64,551)	(84,408)	(70,119)	(51,144)
Ending balance	$ (2,914,544)	$ (2,860,636)	$ (2,759,277)	$ (2,620,725)	$ (2,544,953)	$ (2,485,449)	$ (2,914,544)	$ (2,620,725)