Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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+ Details

Significant Customers (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
Significant Customers (Details) - USD ($) $ in Millions	Dec. 27, 2020	Sep. 27, 2020	Jun. 28, 2020	Mar. 29, 2020	Dec. 29, 2019	Sep. 29, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 27, 2020	Dec. 29, 2019	Dec. 30, 2018
Revenue, Major Customer [Line Items]
Revenue	$ 206.4	$ 202.0	$ 170.4	$ 168.9	$ 185.1	$ 184.1	$ 187.9	$ 160.4	$ 747.7	$ 717.5	$ 618.0
KGS
Revenue, Major Customer [Line Items]
Revenue									560.7	556.1
U.S. Government \| KGS
Revenue, Major Customer [Line Items]
Revenue									$ 546.4	$ 507.4	$ 447.0
Sales to the U.S. Government, percentage of total revenue (percent)									73.00%	71.00%	72.00%