Revenue and Contract Balances - Summary of Contract Liabilities/Assets (Details) - USD ($) $ in Thousands	Dec. 27, 2020	Sep. 27, 2020
Revenue from Contract with Customer [Abstract]
Contract assets	$ 91,598	$ 92,632
Contract liabilities	(199,297)	(171,905)
Net contract liabilities	(107,699)	(79,273)
Disaggregation of Revenue [Line Items]
Contract assets	91,598	92,632
Contract Retentions
Revenue from Contract with Customer [Abstract]
Contract assets	8,500	12,300
Disaggregation of Revenue [Line Items]
Contract assets	$ 8,500	$ 12,300