Segment Information - Narrative (Details) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 27, 2020 USD ($)	Sep. 27, 2020 USD ($)	Jun. 28, 2020 USD ($)	Mar. 29, 2020 USD ($)	Dec. 29, 2019 USD ($)	Sep. 29, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 27, 2020 USD ($) Segment	Dec. 29, 2019 USD ($)	Dec. 30, 2018 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | Segment									2
Total revenues	$ 206.4	$ 202.0	$ 170.4	$ 168.9	$ 185.1	$ 184.1	$ 187.9	$ 160.4	$ 747.7	$ 717.5	$ 618.0
Percentage of foreign revenue to total revenue (as a percent)									19.00%	18.00%	19.00%
Kratos Government Solutions
Segment Reporting Information [Line Items]
Total revenues									$ 560.7	$ 556.1
Assets of foreign subsidiaries	$ 148.2				$ 124.7				148.2	124.7	$ 126.7
Non-US
Segment Reporting Information [Line Items]
Total revenues									$ 139.5	$ 132.5	$ 114.3