Segment Reporting (Detail) - USD ($) $ in Thousands	3 Months Ended
Apr. 03, 2026	Apr. 04, 2025
Segment Reporting Information [Line Items]
Revenues	$ 166,303	$ 145,507
Compensation and related expenses	91,409	75,903
Operating Income	41,379	44,432
Capital Expenditures	2,409	1,252
Depreciation and Amortization	2,515	2,492
Operating segments
Segment Reporting Information [Line Items]
Compensation and related expenses	76,955	69,696
Operating Income	58,800	53,811
Capital Expenditures	671	537
Depreciation and Amortization	1,894	1,873
Corporate
Segment Reporting Information [Line Items]
Compensation and related expenses	14,454	6,207
Operating Income	(17,421)	(9,379)
Capital Expenditures	1,738	715
Depreciation and Amortization	621	619
Engineering and Other Scientific \| Operating segments
Segment Reporting Information [Line Items]
Revenues	141,412	122,135
Compensation and related expenses	64,058	57,248
Operating Income	50,415	45,113
Capital Expenditures	632	475
Depreciation and Amortization	1,849	1,826
Environmental and Health \| Operating segments
Segment Reporting Information [Line Items]
Revenues	24,891	23,372
Compensation and related expenses	12,897	12,448
Operating Income	8,385	8,698
Capital Expenditures	39	62
Depreciation and Amortization	$ 45	$ 47

The current period expense charged against earnings on long-lived, physical assets not used in production, and which are not intended for resale, to allocate or recognize the cost of such assets over their useful lives; or to record the reduction in book value of an intangible asset over the benefit period of such asset; or to reflect consumption during the period of an asset that is not used in production.

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