Acquisitions - Pro Forma Financial Information (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 27, 2020	Sep. 29, 2019	Sep. 27, 2020	Sep. 29, 2019
Business Acquisition [Line Items]
Pro forma net income attributable to Kratos	$ 2.4	$ 2.5	$ 1.5	$ 9.5
FTT
Business Acquisition [Line Items]
Pro forma revenues				540.5
Pro forma net income before tax				10.6
Pro forma net income				11.8
Pro forma net income attributable to Kratos				$ 11.6
Basic pro forma income per share attributable to Kratos (USD per share)				$ 0.11
Diluted pro forma income per share attributable to Kratos (USD per share)				$ 0.11
CPI ASC Signal Division, Inc.
Business Acquisition [Line Items]
Pro forma revenues			559.1
Pro forma net income before tax			(0.7)
Pro forma net income			$ (3.4)
Basic pro forma income per share attributable to Kratos (USD per share)			$ (0.03)
Diluted pro forma income per share attributable to Kratos (USD per share)			$ (0.03)