Segment Information (Details) (USD $) In Millions, unless otherwise specified	0 Months Ended	3 Months Ended		9 Months Ended			3 Months Ended		9 Months Ended			3 Months Ended		9 Months Ended			3 Months Ended		9 Months Ended						0 Months Ended		3 Months Ended
	Feb. 11, 2011	Sep. 30, 2012	Sep. 25, 2011	Sep. 30, 2012 Segment	Sep. 25, 2011	Dec. 25, 2011	Sep. 30, 2012 Kratos Government Solutions	Sep. 25, 2011 Kratos Government Solutions	Sep. 30, 2012 Kratos Government Solutions	Sep. 25, 2011 Kratos Government Solutions	Dec. 25, 2011 Kratos Government Solutions	Sep. 30, 2012 Public Safety and Security	Sep. 25, 2011 Public Safety and Security	Sep. 30, 2012 Public Safety and Security	Sep. 25, 2011 Public Safety and Security	Dec. 25, 2011 Public Safety and Security	Sep. 30, 2012 Unallocated corporate expense, net	Sep. 25, 2011 Unallocated corporate expense, net	Sep. 30, 2012 Unallocated corporate expense, net	Sep. 25, 2011 Unallocated corporate expense, net	Sep. 30, 2012 Discontinued operations	Dec. 25, 2011 Discontinued operations	Sep. 30, 2012 Corporate activities	Dec. 25, 2011 Corporate activities	Jul. 02, 2012 Composite Engineering, Inc.	May 14, 2012 Composite Engineering, Inc.	Sep. 30, 2012 Composite Engineering, Inc.
Segment Reporting Information [Line Items]
Proceeds from the issuance of common stock	$ 61.1			$ 97.0	$ 61.1																					$ 97.0
Number of principal business segments				2
Revenues		276.3	206.6	705.6	500.5		223.5	174.2	568.2	416.9		52.8	32.4	137.4	83.6												34.7
Operating income		14.1	9.7	30.6	19.8		14.0	10.5	32.4	26.8		3.3	3.7	7.3	6.6		(3.2)	(4.5)	(9.1)	(13.6)							1.7
Total assets		$ 1,372.9		$ 1,372.9		$ 1,216.0	$ 1,187.8		$ 1,187.8		$ 1,028.8	$ 127.7		$ 127.7		$ 88.6					$ 6.8	$ 12.2	$ 50.6	$ 86.4
Common stock issued for acquisitions				4.0	10.4																				4.0	20.0