Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Total
Balances at Dec. 31, 2017	$ 1,671	$ 310,811	$ 3,803,844	$ (2,277,001)	$ 1,839,325
Comprehensive income:
Net earnings			118,142		118,142
Cash dividend declared and paid			(26,341)		(26,341)
Share-based compensation		12,036			12,036
Restricted share issuances, net of stock repurchased for payroll taxes		(136)		37	(99)
Balances at Mar. 31, 2018	1,671	322,711	3,895,645	(2,276,964)	1,943,063
Balances at Dec. 31, 2018	1,671	340,457	4,188,435	(2,429,179)	2,101,384
Comprehensive income:
Net earnings			119,601		119,601
Cash dividend declared and paid			(28,272)		(28,272)
Share-based compensation		13,571			13,571
Restricted share issuances, net of stock repurchased for payroll taxes		(2,147)		(373)	(2,520)
Balances at Mar. 31, 2019	$ 1,671	$ 351,881	$ 4,279,764	$ (2,429,552)	$ 2,203,764