Reportable Segments - Revenue by Contract Type (Details) - USD ($) $ in Thousands	3 Months Ended
	Apr. 02, 2022	Apr. 03, 2021
Segment Reporting, Revenue Reconciling Item [Line Items]
Gross revenues	$ 190,154	$ 153,095
INF
Segment Reporting, Revenue Reconciling Item [Line Items]
Gross revenues	99,963	87,533
BTS
Segment Reporting, Revenue Reconciling Item [Line Items]
Gross revenues	60,454	38,605
GEO
Segment Reporting, Revenue Reconciling Item [Line Items]
Gross revenues	29,737	26,957
Cost-reimbursable contracts
Segment Reporting, Revenue Reconciling Item [Line Items]
Gross revenues	164,856	138,983
Cost-reimbursable contracts | INF
Segment Reporting, Revenue Reconciling Item [Line Items]
Gross revenues	95,725	83,385
Cost-reimbursable contracts | BTS
Segment Reporting, Revenue Reconciling Item [Line Items]
Gross revenues	39,487	28,709
Cost-reimbursable contracts | GEO
Segment Reporting, Revenue Reconciling Item [Line Items]
Gross revenues	29,644	26,889
Fixed-unit price contracts
Segment Reporting, Revenue Reconciling Item [Line Items]
Gross revenues	25,298	14,112
Fixed-unit price contracts | INF
Segment Reporting, Revenue Reconciling Item [Line Items]
Gross revenues	4,238	4,148
Fixed-unit price contracts | BTS
Segment Reporting, Revenue Reconciling Item [Line Items]
Gross revenues	20,967	9,896
Fixed-unit price contracts | GEO
Segment Reporting, Revenue Reconciling Item [Line Items]
Gross revenues	$ 93	$ 68