Revenue Recognition - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 26, 2021	Sep. 27, 2020	Sep. 26, 2021	Sep. 27, 2020
Disaggregation of Revenue [Line Items]
Total Revenues	$ 200.6	$ 202.0	$ 599.9	$ 541.3
Kratos Government Solutions
Disaggregation of Revenue [Line Items]
Total Revenues	139.3	148.5	422.4	403.8
Kratos Government Solutions | U.S. Government
Disaggregation of Revenue [Line Items]
Total Revenues	86.4	98.7	270.8	273.4
Kratos Government Solutions | International
Disaggregation of Revenue [Line Items]
Total Revenues	34.9	34.5	102.4	87.4
Kratos Government Solutions | U.S. Commercial and other customers
Disaggregation of Revenue [Line Items]
Total Revenues	18.0	15.3	49.2	43.0
Kratos Government Solutions | Fixed price
Disaggregation of Revenue [Line Items]
Total Revenues	109.8	113.3	316.4	315.9
Kratos Government Solutions | Cost plus fee
Disaggregation of Revenue [Line Items]
Total Revenues	19.6	27.7	76.2	62.9
Kratos Government Solutions | Time and materials
Disaggregation of Revenue [Line Items]
Total Revenues	9.9	7.5	29.8	25.0
Unmanned Systems
Disaggregation of Revenue [Line Items]
Total Revenues	61.3	53.5	177.5	137.5
Unmanned Systems | U.S. Government
Disaggregation of Revenue [Line Items]
Total Revenues	57.3	46.6	161.3	125.4
Unmanned Systems | International
Disaggregation of Revenue [Line Items]
Total Revenues	3.6	6.5	15.4	11.4
Unmanned Systems | U.S. Commercial and other customers
Disaggregation of Revenue [Line Items]
Total Revenues	0.4	0.4	0.8	0.7
Unmanned Systems | Fixed price
Disaggregation of Revenue [Line Items]
Total Revenues	41.2	39.6	114.8	95.5
Unmanned Systems | Cost plus fee
Disaggregation of Revenue [Line Items]
Total Revenues	19.6	12.9	60.9	39.8
Unmanned Systems | Time and materials
Disaggregation of Revenue [Line Items]
Total Revenues	$ 0.5	$ 1.0	$ 1.8	$ 2.2