Value of equity interests (such as common shares, preferred shares, or partnership interest) issued or issuable to acquire the entity.

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-Publisher FASB
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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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Amount of tangible or intangible assets, including a business or subsidiary of the acquirer transferred by the entity to the former owners of the acquiree. Excludes cash.

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Costs incurred to effect a business combination which have been expensed during the period. Such costs could include business integration costs, systems integration and conversion costs, and severance and other employee-related costs.

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The cash inflow associated with the acquisition of business during the period (for example, cash that was held by the acquired business).

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-Publisher FASB
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Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

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The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price.

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Business Combinations Narrative (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Jan. 05, 2018
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross	$ 802,500
Goodwill acquired	572,499
SIlver Spring Networks, Inc. [Member]
Business Acquisition [Line Items]
Cash Acquired from Acquisition	97,800
Business Acquisition, Equity Interest Issued or Issuable, Value Assigned			$ 6,700
Goodwill acquired	572,500
Business Acquisition, Transaction Costs	15,600
Business Combination, Integration Related Costs	$ 46,800
Comverge [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred, Other		$ 100,000
Cash Acquired from Acquisition		18,200
Goodwill acquired		$ 59,700