Summary of Significant Accounting Policies - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue consisted of tuition	99.00%	99.00%	99.00%
Repayment term	10 years
Loan Processing Fee	$ 1,100	$ 900	$ 1,100
Goodwill	8,222	8,222	8,200
Accrued insurance	2,900
Advertising expenses	38,700	39,700	41,200
Stock based compensation expenses	1,808	2,077	1,440
Tax benefit related to stock-based compensation	452	519	360
Cash and cash equivalents	133,721	76,803	65,442	$ 58,104
Restricted cash	$ 12,256	12,116	$ 15,113	$ 14,055
Percentage of cash basis revenue collected from funds distributed under Title IV programs	68.00%
Percentage of cash basis revenue collected from funds distributed under veterans benefits programs	14.00%
Finance lease liabilities	$ 73	129
Financing obligation	$ 23	131
Revision of Prior Period, Reclassification, Adjustment | Long-term Debt, Current Maturities
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Finance lease liabilities		100
Revision of Prior Period, Reclassification, Adjustment | Long-term Debt
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Financing obligation		$ 100
Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Market interest rates	7.00%
Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Market interest rates	10.00%