Revenue - Contract Balances (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
Jun. 30, 2018	Dec. 31, 2017
Revenue from Contract with Customer [Abstract]
Contract assets	$ 1,412.9	$ 1,755.5
Contract (liabilities)	(3,973.3)	(3,314.2)
Net contract assets (liabilities)	(2,560.4)	(1,558.7)
Contract assets, increase (decrease)	(342.6)
Contract (liabilities), increase (decrease)	(659.1)
Net contract assets (liabilities), increase (decrease)	$ (1,001.7)
Contract assets, increase (decrease), percent	(19.50%)
Contract (liabilities), increase (decrease), percent	(19.90%)
Net contract assets (liabilities), increase (decrease), percent	(64.30%)
Contract assets, increase (decrease) due to acquisitions	$ 5.7
Deferred revenue, revenue recognized	601.4	1,437.7
Performance obligation satisfied in previous periods	$ (21.3)	$ 66.8

Billings in Excess of Cost, Current, Increase (Decrease)

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Billings in Excess of Cost, Current, Increase (Decrease), Percent

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Costs in Excess of Billings (Billings in Excess of Cost), Current, Net

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Costs in Excess of Billings (Billings in Excess of Cost), Current, Net, Increase (Decrease)

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Costs in Excess of Billings (Billings in Excess of Cost), Current, Net, Increase (Decrease), Percent

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Costs in Excess of Billings, Current, Increase (Decrease)

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Costs in Excess of Billings, Current, Increase (Decrease), Percent

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Liability attributable to (i) billings in excess of costs under the percentage of completion contract accounting method representing the difference between contractually invoiced amounts (billings) and revenue recognized based, for example, on costs incurred to estimated total costs at period end or (ii) contractually invoiced amounts (billings) in excess of costs incurred and accumulated under the completed contract accounting method that are expected to be realized within one year or one operating cycle, whichever is longer, from the reporting date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 605
-SubTopic 35
-Section 45
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Amount of increase (decrease) in right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time, from business combination.

+ References

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-Publisher FASB
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-Section 50
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Amount of revenue recognized from performance obligation satisfied or partially satisfied in previous reporting periods. Includes, but is not limited to, change in transaction price.

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-Publisher FASB
-Name Accounting Standards Codification
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Amount of receivable reflecting the cost incurred on uncompleted contracts in excess of related billings which is expected to be collected within one year or the normal operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-URI http://asc.fasb.org/extlink&oid=68068069&loc=d3e57795-111642

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Amount of revenue recognized that was previously reported as deferred or unearned revenue.

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