Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net Earnings	$ 292,536	$ 139,283	$ 135,709
Other Comprehensive Income (Loss):
Foreign Currency Translation Adjustment	1,305	(14)	(427)
Total Other Comprehensive Income (Loss)	1,305	(14)	(427)
Comprehensive Income	$ 293,841	$ 139,269	$ 135,282