CAPITAL STOCK - Summary of Repurchases of Class A Common Stock (Details) $ / shares in Units, $ in Thousands			1 Months Ended		3 Months Ended	12 Months Ended
	Aug. 14, 2024 shares	Aug. 13, 2024 USD ($) $ / shares	Aug. 31, 2024 USD ($) shares	Feb. 29, 2024 USD ($) shares	Jun. 30, 2023 USD ($) $ / shares shares	Sep. 30, 2024 USD ($) $ / shares shares	Sep. 30, 2023 USD ($) $ / shares shares	Sep. 30, 2022 USD ($)
Class Of Stock [Line Items]
Reacquisition cost						$ 244,829	$ 116,578	$ 81,483
Class A
Class Of Stock [Line Items]
Total number of shares repurchased (in shares) | shares						5,866,000	4,152,000
Reacquisition cost						$ 244,828	$ 116,578
Average price per share (in dollars per share) | $ / shares						$ 40.03	$ 28.08
Excise tax as reacquisition cost of share repurchases						$ 2,300	$ 1,100
Class A | Accelerated Share Repurchase Agreement
Class Of Stock [Line Items]
Total number of shares repurchased (in shares) | shares			1,165,710	2,725,707
Stock repurchase program, authorized amount			$ 50,000	$ 100,000
Class A | Accelerated Share Repurchase Agreement | JPMorgan
Class Of Stock [Line Items]
Total number of shares repurchased (in shares) | shares	1,000,000
Stock repurchase program, authorized amount		$ 50,000
Accelerated share repurchases, price per share (in dollars per share) | $ / shares		$ 40.00
Accelerated share repurchases, percentage of initial shares		0.80
Class A | Open Market
Class Of Stock [Line Items]
Total number of shares repurchased (in shares) | shares						974,718
Reacquisition cost						$ 42,900
Class A | Secondary Offerings
Class Of Stock [Line Items]
Total number of shares repurchased (in shares) | shares					1,477,832
Reacquisition cost					$ 36,000		$ 36,000
Average price per share (in dollars per share) | $ / shares					$ 24.36