Revenue from Contracts with Customers - Net Change in Estimate (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 27, 2020 USD ($) positions	Sep. 29, 2019 USD ($) positions	Sep. 27, 2020 USD ($) positions	Sep. 29, 2019 USD ($) positions
Revenue from Contract with Customer [Abstract]
Increase (decrease) in revenue from net changes in transaction prices	$ 1,142	$ 0	$ 834	$ (3,301)
Increase (decrease) in revenue from net changes in input cost estimates	(1,041)	1,734	(1,092)	4,144
Net decrease in revenue from net changes in estimates	$ 101	$ 1,734	$ (258)	$ 843
Number of projects | positions	2	1	4	2
Net change in estimate as a percentage of aggregate revenue for associated projects	0.30%	3.60%	(0.20%)	1.50%