Subsequent Event (Notes)	1 Months Ended
Nov. 06, 2018
Subsequent Event [Member]
Subsequent Event [Line Items]
Subsequent Events [Text Block]	17. SUBSEQUENT EVENTS Holding Company On October 1, 2018, NW Holdings and NW Natural completed a reorganization into a holding company structure. NW Holdings is now the parent holding company of NW Natural, NWN Water, NWN Gas Storage and other subsidiaries previously held by NW Natural. This reorganization was approved by NW Holdings’ and NW Natural’s boards of directors, the Oregon, Washington and California public utility commissions, and NW Natural’s shareholders prior to the reorganization. As part of this reorganization, NW Natural shareholders automatically become shareholders of NW Holdings on a one-for-one share basis with the same number of shares and same relative ownership percentage as shareholders held immediately prior to the reorganization. Credit Agreements On October 2, 2018, NW Holdings entered into a $100.0 million credit agreement, with a feature that allows NW Holdings to request increases in the total commitment amount, up to a maximum of $150.0 million. The maturity date of the agreement is October 2, 2023. The credit agreement permits the issuance of letters of credit in an aggregate amount of up to $40.0 million. On October 2, 2018, NW Natural entered into a new multi-year credit agreement for unsecured revolving loans totaling $300.0 million, up to a maximum of $450.0 million, with a maturity date of October 2, 2023 and an available extension of commitments for two additional one-year periods, subject to lender approval (New Credit Agreement). The prior credit agreement was terminated upon the closing of this new agreement. The New Credit Agreement permits the issuance of letters of credit in an aggregate amount of up to $60.0 million. The principal amount of borrowings under the credit agreements are due and payable on the maturity date. The credit agreements require NW Holdings and NW Natural to maintain a consolidated indebtedness to total capitalization ratio of 70% or less. Failure to comply with this covenant would entitle the lenders to terminate their lending commitments and accelerate the maturity of all amounts outstanding. The agreements also require NW Holdings and NW Natural to maintain credit ratings with Standard & Poor's (S&P) and Moody's Investors Service, Inc. (Moody’s) and notify the lenders of any change in the respective companies' senior unsecured debt ratings or senior secured debt ratings, as applicable, by such rating agencies, provided, however that in the event NW Holdings does not have a credit rating, its debt rating will be determined by a formula using NW Natural's credit rating. A change in debt ratings by S&P or Moody’s is not an event of default, nor is the maintenance of a specific minimum level of debt rating a condition of drawing upon the credit agreement. Rather, interest rates on any loans outstanding under the credit agreements are tied to debt ratings and therefore, a change in the debt rating would increase or decrease the cost of any loans under the credit agreements when ratings are changed. Sunriver Agreement On October 12, 2018, NWN Water of Oregon entered into, and NW Holdings guaranteed, an agreement with Sunriver Resort LP to acquire Sunriver Water, LLC and Sunriver Environmental, LLC (Sunriver Acquisition), which are a water utility and wastewater treatment company providing a current combined 9,400 connections at the Sunriver Resort community in Central Oregon. The transaction is expected to close in the first half of 2019. The closing of the transaction is subject to approval by the Public Utility Commission of Oregon and other customary closing conditions.

17. SUBSEQUENT EVENTS

Holding Company

On October 1, 2018, NW Holdings and NW Natural completed a reorganization into a holding company structure. NW Holdings is now the parent holding company of NW Natural, NWN Water, NWN Gas Storage and other subsidiaries previously held by NW Natural.

This reorganization was approved by NW Holdings’ and NW Natural’s boards of directors, the Oregon, Washington and California public utility commissions, and NW Natural’s shareholders prior to the reorganization.

As part of this reorganization, NW Natural shareholders automatically become shareholders of NW Holdings on a one-for-one share basis with the same number of shares and same relative ownership percentage as shareholders held immediately prior to the reorganization.

Credit Agreements

On October 2, 2018, NW Holdings entered into a $100.0 million credit agreement, with a feature that allows NW Holdings to request increases in the total commitment amount, up to a maximum of $150.0 million. The maturity date of the agreement is October 2, 2023. The credit agreement permits the issuance of letters of credit in an aggregate amount of up to $40.0 million.

On October 2, 2018, NW Natural entered into a new multi-year credit agreement for unsecured revolving loans totaling $300.0 million, up to a maximum of $450.0 million, with a maturity date of October 2, 2023 and an available extension of commitments for two additional one-year periods, subject to lender approval (New Credit Agreement). The prior credit agreement was terminated upon the closing of this new agreement. The New Credit Agreement permits the issuance of letters of credit in an aggregate amount of up to $60.0 million.

The principal amount of borrowings under the credit agreements are due and payable on the maturity date. The credit agreements require NW Holdings and NW Natural to maintain a consolidated indebtedness to total capitalization ratio of 70% or less. Failure to comply with this covenant would entitle the lenders to terminate their lending commitments and accelerate the maturity of all amounts outstanding.

The agreements also require NW Holdings and NW Natural to maintain credit ratings with Standard & Poor's (S&P) and Moody's Investors Service, Inc. (Moody’s) and notify the lenders of any change in the respective companies' senior unsecured debt ratings or senior secured debt ratings, as applicable, by such rating agencies, provided, however that in the event NW Holdings does not have a credit rating, its debt rating will be determined by a formula using NW Natural's credit rating. A change in debt ratings by S&P or Moody’s is not an event of default, nor is the maintenance of a specific minimum level of debt rating a condition of drawing upon the credit agreement. Rather, interest rates on any loans outstanding under the credit agreements are tied to debt ratings and therefore, a change in the debt rating would increase or decrease the cost of any loans under the credit agreements when ratings are changed.

Sunriver Agreement

On October 12, 2018, NWN Water of Oregon entered into, and NW Holdings guaranteed, an agreement with Sunriver Resort LP to acquire Sunriver Water, LLC and Sunriver Environmental, LLC (Sunriver Acquisition), which are a water utility and wastewater treatment company providing a current combined 9,400 connections at the Sunriver Resort community in Central Oregon.

The transaction is expected to close in the first half of 2019. The closing of the transaction is subject to approval by the Public Utility Commission of Oregon and other customary closing conditions.