Segment Information - Revenues, Operating Income (Loss) and Assets by Reportable Segments (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 30, 2018	Sep. 30, 2018	Jul. 01, 2018	Apr. 01, 2018	Dec. 31, 2017	Oct. 01, 2017	Jun. 25, 2017	Mar. 26, 2017	Dec. 30, 2018	Dec. 31, 2017	Dec. 25, 2016
Segment Reporting Information [Line Items]
Total revenues	$ 164.4	$ 159.4	$ 151.2	$ 143.0	$ 166.3	$ 157.1	$ 147.9	$ 132.0	$ 618.0	$ 603.3	$ 541.9
Depreciation and amortization									17.9	22.2	22.5
Total operating income (loss) from continuing operations	10.8	$ 10.1	$ 2.6	$ 7.0	(15.0)	$ 0.1	$ 1.5	$ 1.4	30.5	(12.0)	(18.0)
Total assets	1,010.1				1,024.0				1,010.1	1,024.0	948.6
Discontinued Operations [Member]
Segment Reporting Information [Line Items]
Total assets	8.3				97.4				8.3	97.4	92.0
Kratos Government Solutions
Segment Reporting Information [Line Items]
Total revenues									485.1
Unmanned Systems
Segment Reporting Information [Line Items]
Total revenues									132.9
Operating Segments | Kratos Government Solutions
Segment Reporting Information [Line Items]
Total revenues									485.1	481.6	466.1
Depreciation and amortization									13.2	14.4	15.0
Total operating income (loss) from continuing operations									35.5	(0.1)	15.5
Total assets	602.8				597.9				602.8	597.9	609.8
Operating Segments | Unmanned Systems
Segment Reporting Information [Line Items]
Total revenues									132.9	121.7	75.8
Depreciation and amortization									4.7	7.8	7.5
Total operating income (loss) from continuing operations									5.1	(3.6)	(28.3)
Total assets	220.9				201.9				220.9	201.9	172.1
Corporate activities
Segment Reporting Information [Line Items]
Total operating income (loss) from continuing operations									(10.1)	(8.3)	(5.2)
Total assets	$ 178.1				$ 126.8				178.1	126.8	74.7
Service
Segment Reporting Information [Line Items]
Total revenues									200.7	197.8	221.3
Service | Operating Segments | Kratos Government Solutions
Segment Reporting Information [Line Items]
Total revenues									200.7	197.8	221.3
Service | Operating Segments | Unmanned Systems
Segment Reporting Information [Line Items]
Total revenues									0.0	0.0	0.0
Product
Segment Reporting Information [Line Items]
Total revenues									417.3	405.5	320.6
Product | Operating Segments | Kratos Government Solutions
Segment Reporting Information [Line Items]
Total revenues									284.4	283.8	244.8
Product | Operating Segments | Unmanned Systems
Segment Reporting Information [Line Items]
Total revenues									$ 132.9	$ 121.7	$ 75.8