Quarterly Financial Data (Unaudited) Summarized Quarterly Financial Information (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 29, 2019	Sep. 29, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 30, 2018	Sep. 30, 2018	Jul. 01, 2018	Apr. 01, 2018	Dec. 29, 2019	Dec. 30, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Total revenues	$ 185.1	$ 184.1	$ 187.9	$ 160.4	$ 164.4	$ 159.4	$ 151.2	$ 143.0	$ 717.5	$ 618.0	$ 603.3
Gross profit	48.4	48.6	48.1	44.9	45.5	44.1	39.3	40.8	190.0	169.7	157.6
Total operating income (loss)	9.3	11.5	9.0	8.2	10.8	10.1	2.6	7.0	38.0	30.5	(12.0)
Provision (benefit) for income taxes from continuing operations	1.0	2.8	2.5	(1.5)	0.2	3.4	0.1	0.9	4.8	4.6	(10.2)
Income from continuing operations	3.3	2.6	1.3	3.7	5.2	1.4	(3.8)	1.3
Income (loss) from discontinued operations	(0.7)	0.0	3.0	(0.6)	(0.5)	0.3	(3.9)	(3.5)
Net income (loss)	2.6	2.6	4.3	3.1	$ 4.7	$ 1.7	$ (7.7)	$ (2.2)	12.6	(3.5)	(42.7)
Less: Net income attributable to noncontrolling interest	(0.4)	0.1	0.4	0.0					0.1	0.0	0.0
Net income (loss) attributable to Kratos	$ 3.0	$ 2.5	$ 3.9	$ 3.1					$ 12.5	$ (3.5)	$ (42.7)
Basic income (loss) per common share:
Income (loss) from continuing operations (in dollars per share)	$ 0.03	$ 0.02	$ 0.01	$ 0.04	$ 0.05	$ 0.01	$ (0.04)	$ 0.01	$ 0.10	$ 0.04	$ (0.52)
Income (loss) from discontinued operations (in dollars per share)	0	0	0.03	(0.01)	0	0.01	(0.03)	(0.03)	0.02	(0.07)	0.04
Net income (loss) per common share (in dollars per share)	0.03	0.02	0.04	0.03	0.05	0.02	(0.07)	(0.02)	0.12	(0.03)	(0.48)
Diluted income (loss) per common share:
Income (loss) from continuing operations (in dollars per share)	0.03	0.02	0.01	0.03	0.05	0.01	(0.04)	0.01	0.10	0.04	(0.52)
Income (loss) from discontinued operations (in dollars per share)	0	0	0.03	0	(0.01)	0.01	(0.03)	(0.03)	0.01	(0.07)	0.04
Net income (loss) per common share (in dollars per share)	$ 0.03	$ 0.02	$ 0.04	$ 0.03	$ 0.04	$ 0.02	$ (0.07)	$ (0.02)	$ 0.11	$ (0.03)	$ (0.48)