Goodwill and Intangible Assets - Goodwill (Details) $ in Thousands	9 Months Ended
	Jun. 30, 2024 USD ($)
Goodwill
Balance at beginning of the period	$ 1,880,244
Acquisition activity	84,865
Translation and other adjustments	27,001
Balance at end of the period	1,992,110
GSG
Goodwill
Balance at beginning of the period	659,942
Acquisition activity	84,865
Translation and other adjustments	2,282
Balance at end of the period	747,089
CIG
Goodwill
Balance at beginning of the period	1,220,302
Acquisition activity	0
Translation and other adjustments	24,719
Balance at end of the period	$ 1,245,021