Commitments and Contingencies - Summary of Environmental Reserves and Recoveries (Details) - Reserve for Environmental Costs [Member] - USD ($) $ in Millions	1 Months Ended	12 Months Ended
Dec. 31, 2015	Dec. 31, 2016	Nov. 30, 2015	Nov. 30, 2014
Valuation and Qualifying Accounts Disclosure [Line Items]
Estimated recoverable amounts under U.S. government contracts and Northrop	$ 0.6	$ 69.1	$ 159.3	$ 22.9
Expense (benefit) to consolidated statement of operations	(0.1)	18.3	17.3	10.8
Total environmental reserve adjustments	$ 0.5	$ 87.4	$ 176.6	$ 33.7

Amount of the estimated recovery from third parties recorded in the period for an individual site that reduces environmental remediation expense.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 30
-Section 50
-Paragraph 10
-Subparagraph (d)(3)
-URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13237-110859

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 30
-Section 50
-Paragraph 12
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13296-110859

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- Definition

Amount of increase in the allowances and reserves, which consist of the valuation and qualifying accounts that are either netted against the cost of an asset or that reflect a liability established to represent expected future costs, from charges to costs and expenses.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SX 210.12-09)
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24092-122690

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- Definition

Amount of increase (decrease) in allowances and reserves, the valuation and qualifying accounts that are either netted against the cost of an asset or that reflect a liability established to represent expected future costs.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24092-122690

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- Definition

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.

+ References

No definition available.

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