Revenue Recognition - Summary of Revenues (Detail) - Sales Revenue, Net [Member] - Revenue from Rights Concentration Risk [Member]	3 Months Ended		6 Months Ended
	Jun. 28, 2024	Jun. 30, 2023	Jun. 28, 2024	Jun. 30, 2023
Time And Materials Contracts [Member]
Disaggregation Of Revenue [Line Items]
Concentration Risk, Percentage	77.00%	79.00%	80.00%	79.00%
Time And Materials Contracts [Member] | Engineering and Other Scientific [Member]
Disaggregation Of Revenue [Line Items]
Concentration Risk, Percentage	62.00%	64.00%	64.00%	64.00%
Time And Materials Contracts [Member] | Environmental and Health [Member]
Disaggregation Of Revenue [Line Items]
Concentration Risk, Percentage	15.00%	15.00%	16.00%	15.00%
Fixed Price Contracts [Member]
Disaggregation Of Revenue [Line Items]
Concentration Risk, Percentage	23.00%	21.00%	20.00%	21.00%
Fixed Price Contracts [Member] | Engineering and Other Scientific [Member]
Disaggregation Of Revenue [Line Items]
Concentration Risk, Percentage	22.00%	19.00%	19.00%	19.00%
Fixed Price Contracts [Member] | Environmental and Health [Member]
Disaggregation Of Revenue [Line Items]
Concentration Risk, Percentage	1.00%	2.00%	1.00%	2.00%