REVENUE RECOGNITION - Schedule of Revenue by Customer Type and Revenue Concentration Greater than 10% of Total Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Disaggregation of Revenue [Line Items]
Total revenue	$ 36,186	$ 63,593	$ 104,319	$ 169,544
Revenue from Contract with Customer, Product and Service Benchmark | Customer Concentration Risk
Disaggregation of Revenue [Line Items]
Total revenue	$ 36,186	$ 63,593	$ 104,319	$ 169,544
Concentration risk, percentage	100.00%	100.00%	100.00%	100.00%
Revenue from Contract with Customer, Product and Service Benchmark | Customer Concentration Risk | Firm fixed-price
Disaggregation of Revenue [Line Items]
Total revenue	$ 27,809	$ 54,055	$ 80,116	$ 140,636
Concentration risk, percentage	77.00%	85.00%	77.00%	83.00%
Revenue from Contract with Customer, Product and Service Benchmark | Customer Concentration Risk | Time-and-materials
Disaggregation of Revenue [Line Items]
Total revenue	$ 3,504	$ 3,457	$ 10,608	$ 9,104
Concentration risk, percentage	10.00%	5.00%	10.00%	5.00%
Revenue from Contract with Customer, Product and Service Benchmark | Customer Concentration Risk | Cost plus fixed-fee
Disaggregation of Revenue [Line Items]
Total revenue	$ 4,873	$ 6,081	$ 13,595	$ 19,804
Concentration risk, percentage	13.00%	10.00%	13.00%	12.00%
Federal | Revenue from Contract with Customer, Product and Service Benchmark | Customer Concentration Risk
Disaggregation of Revenue [Line Items]
Total revenue	$ 32,955	$ 60,294	$ 93,456	$ 160,351
Concentration risk, percentage	91.00%	95.00%	90.00%	95.00%
State & local, and commercial | Revenue from Contract with Customer, Product and Service Benchmark | Customer Concentration Risk
Disaggregation of Revenue [Line Items]
Total revenue	$ 3,231	$ 3,299	$ 10,863	$ 9,193
Concentration risk, percentage	9.00%	5.00%	10.00%	5.00%
U.S. Department of Defense ("DoD") | Revenue from Contract with Customer, Product and Service Benchmark | Customer Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration risk, percentage	61.00%	77.00%	65.00%	74.00%