Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement of Comprehensive Income [Abstract]
Net earnings	$ 516,361	$ 494,150	$ 448,636
Other comprehensive (loss) income, net of tax:
Foreign currency translation adjustments (net of tax of $0 in 2015, 2014, and 2013)	(38,567)	(18,683)	(7,354)
Change in marketable securities (net of tax of $0 in 2015, 2014, and 2013)	0	(254)	98
Comprehensive income	$ 477,794	$ 475,213	$ 441,380