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	118,545	$ 30	118,515			118,545
Exercise of stock options and release of restricted shares (in shares)		2,956
Shares repurchased under provisions of stock repurchase plans	(407,932)	$ (58)	(146,882)	(260,992)		(407,932)
Shares repurchased under provisions of stock repurchase plans (in shares)		(5,753)
Stock compensation expense	29,269		29,269			29,269
Net earnings	277,146			276,297		276,297	849
Other comprehensive income (loss)	(17,200)				(16,748)	(16,748)	(452)
Dividends paid	(79,180)		159	(79,339)		(79,180)
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
Balance at Mar. 31, 2018	1,982,266	$ 1,743	1,198	2,041,520	(64,992)	1,979,469	2,797
Balance (in shares) at Mar. 31, 2018		174,308
Increase (Decrease) in Equity [Roll Forward]
Exercise of stock options and release of restricted shares	92,148	$ 24	92,124			92,148
Exercise of stock options and release of restricted shares (in shares)		2,360
Shares repurchased under provisions of stock repurchase plans	(235,572)	$ (31)	(109,876)	(125,665)		(235,572)
Shares repurchased under provisions of stock repurchase plans (in shares)		(3,091)
Stock compensation expense	18,002		18,002			18,002
Net earnings	140,946			140,605		140,605	341
Other comprehensive income (loss)	(26,051)				(25,720)	(25,720)	(331)
Dividends paid	(79,180)		159	(79,339)		(79,180)
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]
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	$ 52,803	$ 17	52,786			52,803
Exercise of stock options and release of restricted shares (in shares)		1,656
Shares repurchased under provisions of stock repurchase plans	(234,923)	$ (32)	(79,858)	(155,033)		(234,923)
Shares repurchased under provisions of stock repurchase plans (in shares)		(3,198)
Stock compensation expense	37,206		37,206			37,206
Net earnings	293,641			292,848		292,848	793
Other comprehensive income (loss)	1,131				1,385	1,385	(254)
Dividends paid	(85,184)		403	(85,587)		(85,184)
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	170,040
Balance at Mar. 31, 2019	$ 2,125,434	$ 1,716	3,978	2,222,562	(103,986)	2,124,270	1,164
Balance (in shares) at Mar. 31, 2019		171,648
Increase (Decrease) in Equity [Roll Forward]
Exercise of stock options and release of restricted shares	25,613	$ 11	25,602			25,613
Exercise of stock options and release of restricted shares (in shares)		1,002
Shares repurchased under provisions of stock repurchase plans	(190,589)	$ (26)	(41,374)	(149,189)		(190,589)
Shares repurchased under provisions of stock repurchase plans (in shares)		(2,610)
Stock compensation expense	23,824		23,824			23,824
Net earnings	153,530			153,149		153,149	381
Other comprehensive income (loss)	(234)				(110)	(110)	(124)
Dividends paid	(85,184)		403	(85,587)		(85,184)
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	170,040