Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Statement of Comprehensive Income [Abstract]
Net earnings	$ 119,350	$ 109,320	$ 349,407	$ 321,820
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments (net of tax of $0 in 2013 and 2012)	3,668	4,598	(3,692)	4,154
Change in marketable securities (net of tax of $0 in 2013 and 2012)	4	56	88	46
Comprehensive income	$ 123,022	$ 113,974	$ 345,803	$ 326,020