Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($)	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Total
Balances at Dec. 31, 2018	$ 1,671,000	$ 340,457,000	$ 4,188,435,000	$ (2,429,179,000)	$ 2,101,384,000
Net earnings	0	0	371,644,000	0	371,644,000
Cash dividend declared and paid	0	0	(84,087,000)	0	(84,087,000)
Purchase of treasury shares	0	0	0	(225,680,000)	(225,680,000)
Share-based compensation	0	42,154,000	0	0	42,154,000
Restricted share issuances, net of stock repurchased for payroll taxes and other	0	(14,668)	0	2,782	(11,886)
Balances at Sep. 30, 2019	1,671,000	367,943,000	4,475,992,000	(2,652,077,000)	2,193,529,000
Balances at Jun. 30, 2019	1,671,000	367,166,000	4,385,391,000	(2,618,872,000)	2,135,356,000
Net earnings	0	0	118,410,000	0	118,410,000
Cash dividend declared and paid	0	0	(27,809,000)	0	(27,809,000)
Purchase of treasury shares	0	0	0	(35,946,000)	(35,946,000)
Share-based compensation	0	13,850,000	0	0	13,850,000
Restricted share issuances, net of stock repurchased for payroll taxes and other	0	(13,073,000)	0	2,741,000	(10,332,000)
Balances at Sep. 30, 2019	1,671,000	367,943,000	4,475,992,000	(2,652,077,000)	2,193,529,000
Balances at Dec. 31, 2019	1,671,000	374,049,000	4,592,938,000	(2,701,629,000)	2,267,029,000
Net earnings	0	0	352,028,000	0	352,028,000
Cash dividend declared and paid	0	0	(85,708,000)	0	(85,708,000)
Purchase of treasury shares	0	0	0	(75,193,000)	(75,193,000)
Share-based compensation	0	48,658,000	0	0	48,658,000
Restricted share issuances, net of stock repurchased for payroll taxes and other	0	(18,370)	0	(1,020)	(19,390)
Balances at Sep. 30, 2020	1,671,000	404,337,000	4,859,258,000	(2,777,842,000)	2,487,424,000
Balances at Jun. 30, 2020	1,671,000	402,653,000	4,762,295,000	(2,775,776,000)	2,390,843,000
Net earnings	0	0	125,496,000	0	125,496,000
Cash dividend declared and paid	0	0	(28,533,000)	0	(28,533,000)
Purchase of treasury shares	0	0	0	0	0
Share-based compensation	0	14,594,000	0	0	14,594,000
Restricted share issuances, net of stock repurchased for payroll taxes and other	0	(12,910,000)	0	(2,066,000)	(14,976,000)
Balances at Sep. 30, 2020	$ 1,671,000	$ 404,337,000	$ 4,859,258,000	$ (2,777,842,000)	$ 2,487,424,000