LONG-TERM DEBT, NET - Additional Information (Details)				3 Months Ended		9 Months Ended
	Feb. 18, 2020 USD ($)	Feb. 13, 2020 USD ($) $ / shares shares	May 09, 2019 USD ($)	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Sep. 30, 2021 USD ($)
Debt Instrument [Line Items]
Long-Term Debt				$ 307,927,000		$ 307,927,000		$ 200,605,000
Amortization of deferred debt issuance costs				263,000	$ 244,000	776,000	$ 719,000
Debt issuance costs, net				2,823,000		2,823,000		$ 3,599,000
Exchangeable notes, fair value				107,453,000		107,453,000
Payments for note hedge transactions	$ 28,676,000
Debt issuance costs incurred				0	0	0	0
Class A Common Stock
Debt Instrument [Line Items]
Warrants outstanding (shares) | shares		3,376,391
Warrants sold in connection with the issuance of the exchangeable notes (in USD per share) | $ / shares		$ 62.88
Proceeds from issuance of warrants		$ 14,669,000
1% Exchangeable Senior Notes due 2025 | Exchangeable Notes
Debt Instrument [Line Items]
Original principal amount	$ 138,000,000			$ 117,000,000		$ 117,000,000
Stated interest rate (percent)	1.00%			1.00%		1.00%
Proceeds from convertible debt	$ 132,762,000
Amortization of deferred debt issuance costs				$ 169,000	$ 149,000	$ 492,000	$ 434,000
Debt issuance costs, net				$ 2,113,000		$ 2,113,000
1% Exchangeable Senior Notes due 2025 | Exchangeable Notes | Class A Common Stock
Debt Instrument [Line Items]
Exchangeable notes, exchange rate, shares per $1000	0.0244666
2020 Senior Secured Credit Facility | Line of Credit
Debt Instrument [Line Items]
Revolving line of credit borrowing capacity			$ 275,000,000
Optional addition to borrowing capacity			50,000,000
Unused commitment fee (percent)						0.30%
Debt covenant, minimum consolidated interest coverage ratio				3.00		3.00
Debt covenant, maximum total leverage ratio				5.00		5.00
Debt covenant, increase to maximum consolidated senior secured leverage ratio during leverage increase period				0.25		0.25
Debt covenant, maximum consolidated senior secured leverage ratio				3.25		3.25
Remaining borrowing capacity				$ 67,594,000		$ 67,594,000
Debt covenant, equity repurchase limit from employees, directors, officers or consultants			$ 3,000,000
Debt covenant, dividend or distribution limit as percent of net cash proceeds from additional common equity issuance (percent)			5.00%
2020 Senior Secured Credit Facility | Line of Credit | Minimum
Debt Instrument [Line Items]
Unused commitment fee (percent)						0.15%
2020 Senior Secured Credit Facility | Line of Credit | Maximum
Debt Instrument [Line Items]
Unused commitment fee (percent)						0.30%
2020 Senior Secured Credit Facility | Line of Credit | One, Two, Three or Six-month LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (percent)						3.25%
2020 Senior Secured Credit Facility | Line of Credit | One, Two, Three or Six-month LIBOR | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate (percent)						2.25%
2020 Senior Secured Credit Facility | Line of Credit | One, Two, Three or Six-month LIBOR | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate (percent)						3.25%
2020 Senior Secured Credit Facility | Line of Credit | Federal Funds Rate
Debt Instrument [Line Items]
Basis spread on variable rate (percent)						0.50%
2020 Senior Secured Credit Facility | Line of Credit | LIBOR plus 1%
Debt Instrument [Line Items]
Basis spread on variable rate (percent)						1.25%
2020 Senior Secured Credit Facility | Line of Credit | LIBOR plus 1% | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate (percent)						0.25%
2020 Senior Secured Credit Facility | Line of Credit | LIBOR plus 1% | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate (percent)						1.25%
2020 Senior Secured Credit Facility | Line of Credit | 30-day LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (percent)						1.00%
2020 Senior Secured Credit Facility | Line of Credit | Letter of Credit | Maximum
Debt Instrument [Line Items]
Unused commitment fee (percent)						3.25%