Segment Information - Schedule of Segment Revenues, Depreciation and Amortization, and Operating (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 26, 2021	Sep. 27, 2020	Sep. 26, 2021	Sep. 27, 2020
Segment Reporting Information [Line Items]
Total revenues	$ 200.6	$ 202.0	$ 599.9	$ 541.3
Depreciation & amortization:
Total depreciation and amortization	6.1	6.2	19.4	18.5
Operating income from continuing operations:
Total operating income from continuing operations	10.5	12.7	18.7	20.3
Corporate activities
Operating income from continuing operations:
Total operating income from continuing operations	(6.7)	(5.1)	(19.8)	(16.0)
Kratos Government Solutions
Segment Reporting Information [Line Items]
Total revenues	139.3	148.5	422.4	403.8
Depreciation & amortization:
Total depreciation and amortization	4.3	4.5	13.2	13.6
Kratos Government Solutions | Reportable Segments
Operating income from continuing operations:
Total operating income from continuing operations	14.6	14.1	27.6	31.1
Unmanned Systems
Segment Reporting Information [Line Items]
Total revenues	61.3	53.5	177.5	137.5
Depreciation & amortization:
Total depreciation and amortization	1.8	1.7	6.2	4.9
Unmanned Systems | Reportable Segments
Operating income from continuing operations:
Total operating income from continuing operations	2.6	3.7	10.9	5.2
Service revenues
Segment Reporting Information [Line Items]
Total revenues	51.6	67.6	166.9	194.1
Service revenues | Kratos Government Solutions
Segment Reporting Information [Line Items]
Total revenues	50.5	67.6	163.3	194.1
Service revenues | Unmanned Systems
Segment Reporting Information [Line Items]
Total revenues	1.1	0.0	3.6	0.0
Product sales
Segment Reporting Information [Line Items]
Total revenues	149.0	134.4	433.0	347.2
Product sales | Kratos Government Solutions
Segment Reporting Information [Line Items]
Total revenues	88.8	80.9	259.1	209.7
Product sales | Unmanned Systems
Segment Reporting Information [Line Items]
Total revenues	$ 60.2	$ 53.5	$ 173.9	$ 137.5