Segment Reporting - Information by Reportable Segment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 26, 2021	Sep. 27, 2020	Sep. 26, 2021	Sep. 27, 2020
Segment Reporting Information [Line Items]
Revenues	$ 689,514	$ 666,240	$ 2,185,279	$ 1,926,795
Operating income (loss)	26,036	28,532	82,993	70,284
Amortization of intangible assets	12,630	8,047	37,476	24,141
Corporate
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Operating income (loss)	(7,514)	(8,548)	(24,409)	(23,027)
Amortization of intangible assets		0	0	0
GMS | Operating Segments
Segment Reporting Information [Line Items]
Revenues	448,078	521,346	1,480,982	1,486,643
Operating income (loss)	20,459	31,401	73,673	75,541
Amortization of intangible assets	4,161	4,115	12,483	12,346
NSS | Operating Segments
Segment Reporting Information [Line Items]
Revenues	241,436	144,894	704,297	440,152
Operating income (loss)	13,091	5,679	33,729	17,770
Amortization of intangible assets	$ 8,469	$ 3,932	$ 24,993	$ 11,795