Fair Value Measurements - Narrative (Details) - Vencore Holding Corp. and KGS Holding Corp. - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Mar. 30, 2018
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Fair value inputs, volatility factor	74.80%	84.10%	51.90%
Fair value inputs, risk-free interest rate	1.39%	0.85%	1.31%
Fair value inputs, discount on lack of marketability	21.00%	33.00%	34.00%
Carrying value
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Long-term debt fair value disclosure	$ 971.0	$ 878.2		$ 969.0
Estimate fair value
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Long-term debt fair value disclosure	$ 993.8	$ 907.1		$ 985.8

Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13433-108611

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13476-108611

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Risk-free interest rate assumption used in valuing an instrument.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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Weighted average expected volatility of stock price.

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Adjustment to the discount rate used to measure fair value for lack of ability to convert business interests into cash quickly.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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