Organization and Summary of Significant Accounting Policies - (Details) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Oct. 01, 2017 USD ($) Segment	Dec. 30, 2018 USD ($) Segment $ / shares	Dec. 31, 2017 USD ($) $ / shares	Dec. 25, 2016 USD ($) $ / shares	Jan. 01, 2019 USD ($)	Jan. 01, 2018 USD ($)	Sep. 25, 2016 USD ($)
Significant Accounting Policies Disclosure [Line Items]
Number of reportable segments | Segment	2	3
Share-based Compensation
Employee Stock Purchase Plan offering & expense recognition period		6 months
Impact on net loss per common share, basic and diluted (in dollars per share) | $ / shares		$ (0.07)	$ (0.09)	$ (0.08)
Allowance for Doubtful Accounts
Provisions		$ 1,800	$ 0	$ 100
Cash and Cash Equivalents
Restricted cash		300	400
Interest Expense, Net
Interest expense incurred primarily on the Company’s Senior Secured Notes		(21,600)	(29,100)	(34,700)
Miscellaneous interest income		800	500	0
Interest expense, net		(20,800)	(28,600)	(34,700)
Foreign Currency
Foreign currency transaction gain (loss)		(1,100)	400	400
Recent Accounting Pronouncements
Accumulated deficit		$ 724,500	720,800
ASC 606
Recent Accounting Pronouncements
Accumulated deficit						$ 721,000
ASC 840 | Subsequent Event
Recent Accounting Pronouncements
Operating lease asset					$ 68,000
Operating lease liability					$ 68,000
ASC 606 Adjustment | ASC 606
Recent Accounting Pronouncements
Accumulated deficit						$ 200
Minimum
Share-based Compensation
Share-based incentive award vesting period		5 years
Goodwill and Other Intangible Assets, Net
Useful life of finite-lived intangible assets		1 year
Maximum
Share-based Compensation
Share-based incentive award vesting period		10 years
Goodwill and Other Intangible Assets, Net
Useful life of finite-lived intangible assets		15 years
Buildings and improvements | Minimum
Property and Equipment, Net
Useful life of property and equipment		15 years
Buildings and improvements | Maximum
Property and Equipment, Net
Useful life of property and equipment		39 years
Machinery and equipment | Minimum
Property and Equipment, Net
Useful life of property and equipment		3 years
Machinery and equipment | Maximum
Property and Equipment, Net
Useful life of property and equipment		10 years
Computer equipment and software | Minimum
Property and Equipment, Net
Useful life of property and equipment		1 year
Computer equipment and software | Maximum
Property and Equipment, Net
Useful life of property and equipment		10 years
Vehicles, furniture, and office equipment | Maximum
Property and Equipment, Net
Useful life of property and equipment		5 years
Allowance for Doubtful Accounts
Allowance for Doubtful Accounts
Balance at Beginning of Year	$ 1,500	$ 500	1,500	1,500
Provisions		1,800	0	100
Write-offs/Recoveries		0	(1,000)	(100)
Balance at End of Year		2,300	500	1,500
Continuing operations
Share-based Compensation
Stock-based compensation expense, amount recognized in the consolidated financial statements		7,200	7,800	5,100
Selling, general and administrative expenses
Share-based Compensation
Stock-based compensation expense, amount recognized in the consolidated financial statements		$ 7,200	7,800	$ 5,100
Kratos Government Solutions (KGS) | Building facility
Property and Equipment, Net
Carrying value of building held-for-sale							$ 1,900
Remeasured fair value of building held-for-sale			500
Impairment loss on building reclassified from held-for-sale to held			$ 1,400
Stock options | Maximum
Share-based Compensation
Share-based incentive award vesting period		6 years