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	$ 490,383	$ 432,533	$ 459,497
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments, net of tax of $16,761 in 2017, $12,687 in 2016 and $23,801 in 2015	30,434	(23,743)	(44,090)
Other comprehensive income (loss)	30,434	(23,743)	(44,090)
Comprehensive income	520,817	408,790	415,407
Less comprehensive income attributable to the noncontrolling interest	844	1,337	1,605
Comprehensive income attributable to shareholders	$ 519,973	$ 407,453	$ 413,802