Goodwill - Roll Forward of Goodwill (Detail) - USD ($) $ in Thousands		3 Months Ended	12 Months Ended
		Sep. 30, 2018	Jun. 30, 2018
Goodwill [Roll Forward]
Balance		$ 2,620,835	$ 2,577,435
Goodwill acquired	[1]	41,955	41,891
Foreign currency translation		(1,388)	1,509
Balance		2,661,402	2,620,835
Domestic
Goodwill [Roll Forward]
Balance		2,514,520	2,479,496
Goodwill acquired	[1]	42,147	35,024
Balance		2,556,667	2,514,520
International
Goodwill [Roll Forward]
Balance		106,315	97,939
Goodwill acquired	[1]	(192)	6,867
Foreign currency translation		(1,388)	1,509
Balance		$ 104,735	$ 106,315

[1] Includes goodwill initially allocated to new business combinations as well as measurement period adjustments.