Leases - Narrative (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2020 USD ($) location	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) location	Jun. 30, 2019 USD ($)	Sep. 30, 2019 USD ($)
Lessee, Lease, Description [Line Items]
Number of lease contracts | location			10
Number of campuses | location	12		12
Retained deficit	$ (38,098)		$ (38,098)		$ (44,673)
Operating lease, rent expense including related parties	500	$ 500	1,500	$ 1,500
Operating lease payments due	176,429		$ 176,429
Minimum annual rent increase, percent			4.00%
John C. White, Property One
Lessee, Lease, Description [Line Items]
Operating lease payments due	300		$ 300
John C. White, Property Two
Lessee, Lease, Description [Line Items]
Operating lease payments due	$ 700		$ 700
Minimum
Lessee, Lease, Description [Line Items]
Lease term	8 years		8 years
Maximum
Lessee, Lease, Description [Line Items]
Lease term	20 years		20 years