Acquisitions - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Mar. 28, 2021	Sep. 27, 2020	Mar. 29, 2020	Mar. 28, 2021	Mar. 29, 2020
Business Acquisition [Line Items]
Contingent earn-out liability	$ 28,700			$ 28,700
Aggregate maximum of contingent consideration	66,900			66,900
Gain on fair value adjustment to contingent consideration	$ 230		$ 1,571	$ 193	$ 1,571
Minimum
Business Acquisition [Line Items]
Significant unobservable input, earn-out period				2 years
Minimum | Existing customer contracts
Business Acquisition [Line Items]
Useful life of intangible assets				1 year
Minimum | Trade names
Business Acquisition [Line Items]
Useful life of intangible assets				3 years
Maximum
Business Acquisition [Line Items]
Significant unobservable input, earn-out period				3 years
Maximum | Existing customer contracts
Business Acquisition [Line Items]
Useful life of intangible assets				10 years
Maximum | Trade names
Business Acquisition [Line Items]
Useful life of intangible assets				5 years
SEG
Business Acquisition [Line Items]
Fair value of acquisition purchase price			40,900
Initial cash payments			29,600
Contingent earn-out liability			11,300		11,300
Aggregate maximum of contingent consideration			$ 20,000		$ 20,000
Earn-out period			3 years
BWF
Business Acquisition [Line Items]
Fair value of acquisition purchase price		$ 47,700
Initial cash payments		41,800
Contingent earn-out liability		5,200
Aggregate maximum of contingent consideration		$ 8,000
Earn-out period		3 years
Payables related to estimated post-closing adjustments		$ 700