Business Overview - Revenues by Customer (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2022	Mar. 31, 2021
Concentration Risk [Line Items]
Revenue	$ 108,699	$ 61,506	$ 261,500	$ 119,358
Department of Homeland Security
Concentration Risk [Line Items]
Revenue	39,978	167
Department of Veterans Affairs
Concentration Risk [Line Items]
Revenue	30,733	27,871
Department of Health and Human Services
Concentration Risk [Line Items]
Revenue	27,584	23,341
Department of Defense
Concentration Risk [Line Items]
Revenue	8,460	7,522
Other customers with less than 10% share of total revenue
Concentration Risk [Line Items]
Revenue	$ 1,944	$ 2,605
Revenue from Contract with Customer | Customer concentration
Concentration Risk [Line Items]
Revenue			$ 261,500	$ 119,358
Percent of total revenue			100.00%	100.00%
Revenue from Contract with Customer | Customer concentration | Department of Homeland Security
Concentration Risk [Line Items]
Revenue			$ 131,306	$ 339
Percent of total revenue			50.20%	0.30%
Revenue from Contract with Customer | Customer concentration | Department of Veterans Affairs
Concentration Risk [Line Items]
Revenue			$ 58,926	$ 55,513
Percent of total revenue			22.50%	46.50%
Revenue from Contract with Customer | Customer concentration | Department of Health and Human Services
Concentration Risk [Line Items]
Revenue			$ 50,710	$ 43,503
Percent of total revenue			19.40%	36.40%
Revenue from Contract with Customer | Customer concentration | Department of Defense
Concentration Risk [Line Items]
Revenue			$ 16,955	$ 14,502
Percent of total revenue			6.50%	12.20%
Revenue from Contract with Customer | Customer concentration | Other customers with less than 10% share of total revenue
Concentration Risk [Line Items]
Revenue			$ 3,603	$ 5,501
Percent of total revenue			1.40%	4.60%