Condensed Consolidated Statements of Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional paid-in capital	Retained earnings	Accumulated other comprehensive loss	Total shareholders' equity	Noncontrolling interest
Balance at Dec. 31, 2017	$ 1,994,373	$ 1,764	$ 546	$ 2,063,512	$ (73,964)	$ 1,991,858	$ 2,515
Balance (in shares) at Dec. 31, 2017		176,374
Increase (Decrease) in Equity [Roll Forward]
Exercise of stock options and release of restricted shares	133,060	$ 33	133,027			133,060
Exercise of stock options and release of restricted shares (in shares)		3,288
Issuance of shares under stock purchase plan	33,292	$ 7	33,285			33,292
Issuance of shares under stock purchase plan (in shares)		666
Shares repurchased under provisions of stock repurchase plan	(555,760)	$ (78)	(208,266)	(347,416)		(555,760)
Shares repurchased under provisions of stock repurchase plans (in shares)		(7,764)
Stock compensation expense	43,171		43,171			43,171
Net earnings	440,213			438,989		438,989	1,224
Other comprehensive income (loss)	(28,129)				(27,134)	(27,134)	(995)
Dividends paid	(79,180)		159	(79,339)		(79,180)
Purchase of noncontrolling interest	(613)		(90)			(90)	(523)
Distributions to noncontrolling interest	(633)						(633)
Balance at Sep. 30, 2018	1,957,332	$ 1,726	1,832	2,053,389	(101,098)	1,955,849	1,483
Balance (in shares) at Sep. 30, 2018		172,564
Balance at Jun. 30, 2018	1,892,559	$ 1,736	1,607	1,977,121	(90,712)	1,889,752	2,807
Balance (in shares) at Jun. 30, 2018		173,577
Increase (Decrease) in Equity [Roll Forward]
Exercise of stock options and release of restricted shares	14,515	$ 3	14,512			14,515
Exercise of stock options and release of restricted shares (in shares)		332
Issuance of shares under stock purchase plan	33,292	$ 7	33,285			33,292
Issuance of shares under stock purchase plan (in shares)		666
Shares repurchased under provisions of stock repurchase plan	(147,828)	$ (20)	(61,384)	(86,424)		(147,828)
Shares repurchased under provisions of stock repurchase plans (in shares)		(2,011)
Stock compensation expense	13,902		13,902			13,902
Net earnings	163,067			162,692		162,692	375
Other comprehensive income (loss)	(10,929)				(10,386)	(10,386)	(543)
Purchase of noncontrolling interest	(613)		(90)			(90)	(523)
Distributions to noncontrolling interest	(633)						(633)
Balance at Sep. 30, 2018	1,957,332	$ 1,726	1,832	2,053,389	(101,098)	1,955,849	1,483
Balance (in shares) at Sep. 30, 2018		172,564
Increase (Decrease) in Equity [Roll Forward]
Cumulative effect of accounting change	(22,462)			(22,357)		(22,357)	(105)
Balance at Dec. 31, 2018	$ 1,987,720	$ 1,716	1,896	2,088,707	(105,481)	1,986,838	882
Balance (in shares) at Dec. 31, 2018	171,582	171,582
Increase (Decrease) in Equity [Roll Forward]
Exercise of stock options and release of restricted shares	$ 75,641	$ 22	75,619			75,641
Exercise of stock options and release of restricted shares (in shares)		2,166
Issuance of shares under stock purchase plan	37,875	$ 6	37,869			37,875
Issuance of shares under stock purchase plan (in shares)		585
Shares repurchased under provisions of stock repurchase plan	(296,922)	$ (42)	(141,847)	(155,033)		(296,922)
Shares repurchased under provisions of stock repurchase plans (in shares)		(4,090)
Stock compensation expense	49,361		49,361			49,361
Net earnings	454,268			453,069		453,069	1,199
Other comprehensive income (loss)	(13,472)				(13,293)	(13,293)	(179)
Dividends paid	(85,184)		403	(85,587)		(85,184)
Balance at Sep. 30, 2019	$ 2,209,287	$ 1,702	23,301	2,301,156	(118,774)	2,207,385	1,902
Balance (in shares) at Sep. 30, 2019	170,243	170,243
Balance at Jun. 30, 2019	$ 2,052,394	$ 1,701	12,433	2,140,935	(104,096)	2,050,973	1,421
Balance (in shares) at Jun. 30, 2019		170,040
Increase (Decrease) in Equity [Roll Forward]
Exercise of stock options and release of restricted shares	22,838	$ 5	22,833			22,838
Exercise of stock options and release of restricted shares (in shares)		510
Issuance of shares under stock purchase plan	37,875	$ 6	37,869			37,875
Issuance of shares under stock purchase plan (in shares)		585
Shares repurchased under provisions of stock repurchase plan	(61,999)	$ (10)	(61,989)			(61,999)
Shares repurchased under provisions of stock repurchase plans (in shares)		(892)
Stock compensation expense	12,155		12,155			12,155
Net earnings	160,627			160,221		160,221	406
Other comprehensive income (loss)	(14,603)				(14,678)	(14,678)	75
Balance at Sep. 30, 2019	$ 2,209,287	$ 1,702	$ 23,301	$ 2,301,156	$ (118,774)	$ 2,207,385	$ 1,902
Balance (in shares) at Sep. 30, 2019	170,243	170,243