Amount recognized for assets, including goodwill, in excess of (less than) the aggregate liabilities assumed.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=84161108&loc=d3e4845-128472

Name:	us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Business Combinations Purchase Price Allocation (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Jan. 05, 2018
Business Acquisition [Line Items]
Customer contract and relationships	$ 0	$ (23,900)
SIlver Spring Networks, Inc. [Member]
Business Acquisition [Line Items]
Total net assets acquired			$ 809,200