Revenue Recognition - Summary of Revenues (Detail) - Sales Revenue, Net [Member] - Revenue from Rights Concentration Risk [Member]	3 Months Ended		9 Months Ended
	Sep. 27, 2024	Sep. 29, 2023	Sep. 27, 2024	Sep. 29, 2023
Time And Materials Contracts [Member]
Disaggregation Of Revenue [Line Items]
Concentration Risk, Percentage	78.00%	76.00%	79.00%	78.00%
Time And Materials Contracts [Member] | Engineering and Other Scientific [Member]
Disaggregation Of Revenue [Line Items]
Concentration Risk, Percentage	63.00%	61.00%	63.00%	63.00%
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	22.00%	24.00%	21.00%	22.00%
Fixed Price Contracts [Member] | Engineering and Other Scientific [Member]
Disaggregation Of Revenue [Line Items]
Concentration Risk, Percentage	21.00%	23.00%	20.00%	20.00%
Fixed Price Contracts [Member] | Environmental and Health [Member]
Disaggregation Of Revenue [Line Items]
Concentration Risk, Percentage	1.00%	1.00%	1.00%	2.00%