Revenue Recognition - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2022	Mar. 31, 2021
Disaggregation of Revenue [Line Items]
Total Revenue	$ 108,699	$ 61,506	$ 261,500	$ 119,358
Revenue from Contract with Customer | Customer concentration
Disaggregation of Revenue [Line Items]
Total Revenue			261,500	119,358
Prime Contractor
Disaggregation of Revenue [Line Items]
Total Revenue	100,012	53,888	246,119	105,652
Subcontractor
Disaggregation of Revenue [Line Items]
Total Revenue	8,687	7,618	15,381	13,706
Time and Materials
Disaggregation of Revenue [Line Items]
Total Revenue	85,860	46,508	218,400	90,702
Cost Reimbursable
Disaggregation of Revenue [Line Items]
Total Revenue	12,275	12,005	22,385	23,726
Firm Fixed Price
Disaggregation of Revenue [Line Items]
Total Revenue	10,564	2,993	20,715	4,930
Department of Homeland Security
Disaggregation of Revenue [Line Items]
Total Revenue	39,978	167
Department of Homeland Security | Revenue from Contract with Customer | Customer concentration
Disaggregation of Revenue [Line Items]
Total Revenue			131,306	339
Department of Veterans Affairs
Disaggregation of Revenue [Line Items]
Total Revenue	30,733	27,871
Department of Veterans Affairs | Revenue from Contract with Customer | Customer concentration
Disaggregation of Revenue [Line Items]
Total Revenue			58,926	55,513
Department of Health and Human Services
Disaggregation of Revenue [Line Items]
Total Revenue	27,584	23,341
Department of Health and Human Services | Revenue from Contract with Customer | Customer concentration
Disaggregation of Revenue [Line Items]
Total Revenue			50,710	43,503
Department of Defense
Disaggregation of Revenue [Line Items]
Total Revenue	8,460	7,522
Department of Defense | Revenue from Contract with Customer | Customer concentration
Disaggregation of Revenue [Line Items]
Total Revenue			16,955	14,502
Other
Disaggregation of Revenue [Line Items]
Total Revenue	$ 1,944	$ 2,605
Other | Revenue from Contract with Customer | Customer concentration
Disaggregation of Revenue [Line Items]
Total Revenue			$ 3,603	$ 5,501