Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net earnings	$ 65,725	$ 61,371	$ 131,452	$ 144,635
Other comprehensive loss:
Foreign currency translation adjustments	3,040	10,437	(10,425)	10,182
Interest rate caps, net of tax	(2,140)	2,310	(4,970)	1,507
Foreign exchange contracts, net of tax	242		(168)
Other comprehensive income (loss), net of tax	1,142	12,747	(15,563)	11,689
Total comprehensive income	$ 66,867	$ 74,118	$ 115,889	$ 156,324