Segment Information - Schedule of Segment Revenues, Depreciation and Amortization, and Operating (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 29, 2019	Sep. 30, 2018	Sep. 29, 2019	Sep. 30, 2018
Segment Reporting Information [Line Items]
Total revenues	$ 184.1	$ 159.4	$ 532.4	$ 453.6
Depreciation & amortization:
Total depreciation and amortization			16.8	13.6
Operating income from continuing operations:
Total operating income from continuing operations	11.5	10.1	28.7	19.7
Kratos Government Solutions
Segment Reporting Information [Line Items]
Total revenues	138.4	126.1	409.3	356.9
Unmanned Systems
Segment Reporting Information [Line Items]
Total revenues	45.7	33.3	123.1	96.7
Reportable Segments
Depreciation & amortization:
Total depreciation and amortization	5.7	4.4	16.8	13.6
Reportable Segments | Kratos Government Solutions
Segment Reporting Information [Line Items]
Total revenues	138.4	126.1	409.3	356.9
Depreciation & amortization:
Total depreciation and amortization	4.5	3.3	13.2	10.2
Operating income from continuing operations:
Total operating income from continuing operations	11.1	11.0	33.2	23.9
Reportable Segments | Unmanned Systems
Segment Reporting Information [Line Items]
Total revenues	45.7	33.3	123.1	96.7
Depreciation & amortization:
Total depreciation and amortization	1.2	1.1	3.6	3.4
Operating income from continuing operations:
Total operating income from continuing operations	3.3	1.0	5.6	3.8
Corporate activities
Operating income from continuing operations:
Total operating income from continuing operations	(2.9)	(1.9)	(10.1)	(8.0)
Service revenues
Segment Reporting Information [Line Items]
Total revenues	70.8	54.9	207.1	147.9
Service revenues | Reportable Segments | Kratos Government Solutions
Segment Reporting Information [Line Items]
Total revenues	70.8	54.9	207.1	147.9
Product sales
Segment Reporting Information [Line Items]
Total revenues	113.3	104.5	325.3	305.7
Product sales | Reportable Segments | Kratos Government Solutions
Segment Reporting Information [Line Items]
Total revenues	$ 67.6	$ 71.2	$ 202.2	$ 209.0