Business Combinations (Details) $ in Thousands	12 Months Ended
Dec. 31, 2018 USD ($) shares	Dec. 31, 2017 USD ($)
Business Acquisition [Line Items]
Business Combination, Control Obtained Description	Through the purchase of all of the outstanding shares of Falls Water, NWN Water acquired the net assets and 100% control of Falls Water.
Goodwill	$ 8,954	$ 0
Falls Water Co [Member]
Business Acquisition [Line Items]
Consideration transferred	$ 8,500
Consideration transferred, shares \| shares	125,000
Connections of acquired business	5,300 connections
Goodwill	$ 6,400
Other insignificant acquisitions [Member]
Business Acquisition [Line Items]
Consideration transferred	$ 2,800
Number of Businesses Acquired	3

Business Acquisition, Connections of Acquired Business

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- Definition

Business Combination, Consideration Transferred, Shares

+ References

No definition available.

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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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- Definition

Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
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- Definition

This element represents a description of how the entity obtained control of the acquired entity.

+ References

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-SubTopic 10
-Section 50
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- Definition

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

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-Publisher FASB
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- Definition

The number of businesses acquired by the entity during the period.

+ References

No definition available.

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