REVENUE RECOGNITION - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Disaggregation of Revenue [Line Items]
Total revenue	$ 63,593	$ 68,981	$ 169,544	$ 178,383
Revenue from Contract with Customer, Product and Service Benchmark | Customer Concentration Risk
Disaggregation of Revenue [Line Items]
Total revenue	63,593	68,981	169,544	178,383
Firm fixed-price | Revenue from Contract with Customer, Product and Service Benchmark | Customer Concentration Risk
Disaggregation of Revenue [Line Items]
Total revenue	$ 54,055	$ 60,349	$ 140,636	$ 155,832
Concentration risk, percentage	85.00%	87.00%	83.00%	87.00%
Time-and-materials | Revenue from Contract with Customer, Product and Service Benchmark | Customer Concentration Risk
Disaggregation of Revenue [Line Items]
Total revenue	$ 3,457	$ 3,154	$ 9,104	$ 9,243
Concentration risk, percentage	5.00%	5.00%	5.00%	5.00%
Cost plus fixed fee | Revenue from Contract with Customer, Product and Service Benchmark | Customer Concentration Risk
Disaggregation of Revenue [Line Items]
Total revenue	$ 6,081	$ 5,478	$ 19,804	$ 13,308
Concentration risk, percentage	10.00%	8.00%	12.00%	8.00%
Federal | Revenue from Contract with Customer, Product and Service Benchmark
Disaggregation of Revenue [Line Items]
Total revenue		$ 66,612
Federal | Revenue from Contract with Customer, Product and Service Benchmark | Customer Concentration Risk
Disaggregation of Revenue [Line Items]
Total revenue	$ 60,294		$ 160,351	$ 171,091
Concentration risk, percentage	95.00%	97.00%	95.00%	96.00%
State & local, and commercial | Revenue from Contract with Customer, Product and Service Benchmark | Customer Concentration Risk
Disaggregation of Revenue [Line Items]
Total revenue	$ 3,299	$ 2,369	$ 9,193	$ 7,292
Concentration risk, percentage	5.00%	3.00%	5.00%	4.00%
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	77.00%	74.00%	74.00%	75.00%
Civilian federal agencies | Revenue from Contract with Customer, Product and Service Benchmark | Customer Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration risk, percentage	18.00%	23.00%	21.00%	21.00%