Business Combinations Business Combinations (Notes)	9 Months Ended
Sep. 30, 2018
Business Combinations [Abstract]
Business Combination Disclosure [Text Block]	13. BUSINESS COMBINATIONS On September 13, 2018, NWN Water, then a wholly-owned subsidiary of NW Natural, completed the acquisition of Falls Water Co., Inc., a privately-owned water utility in the Pacific Northwest for preliminary non-cash consideration of $8.5 million, subject to closing adjustments, in the form of 125,000 shares of NW Natural common stock. Falls Water became a wholly-owned subsidiary of NWN Water and marked its first acquisition in the regulated water utility sector. This acquisition aligns with our water sector strategy as the acquisition provides NWN Water entry into Idaho, expands service area, and opens further opportunity for growth. Falls Water is based in Idaho Falls, Idaho and serves approximately 5,300 connections. Through the purchase of all of the outstanding shares of Falls Water, NWN Water acquired the net assets and 100% control of Falls Water. We determined that the Falls Water acquisition met the criteria of a business combination, and as such performed a preliminary allocation of the consideration to the acquired assets and assumed liabilities based on their fair value as of the acquisition date, the majority of which was allocated to goodwill. The allocation is considered preliminary as we continue to evaluate working capital adjustments, certain tax positions, and goodwill. We do not expect any subsequent adjustments to be significant, and expect any such adjustments to be completed within the one-year measurement period. The acquisition costs were insignificant and were expensed as incurred. The results of Falls Water are not material to the consolidated financial results. Preliminary goodwill of $6.6 million was recognized from this acquisition and is attributable to Falls Water's regulated service territory and experienced workforce as well as the strategic benefits expected from this high-growth service territory. NW Natural has included this goodwill in other for segment reporting purposes, and it is not deductible for income tax purposes. No intangible assets aside from goodwill were acquired. We allocate goodwill to reporting units based on the expected benefit from the business combination. We perform an annual impairment assessment of goodwill at the reporting unit level, or more frequently if events and circumstances indicate that goodwill might be impaired. An impairment loss is recognized if the carrying value of a reporting unit’s goodwill exceeds its fair value. An impairment analysis has not been performed in the current year, since all goodwill was acquired in the Falls Water acquisition, which closed in the third quarter of 2018. We anticipate that an annual impairment assessment of goodwill will occur in the fourth quarter of each year, beginning in the fourth quarter of 2018.

13. BUSINESS COMBINATIONS

On September 13, 2018, NWN Water, then a wholly-owned subsidiary of NW Natural, completed the acquisition of Falls Water Co., Inc., a privately-owned water utility in the Pacific Northwest for preliminary non-cash consideration of $8.5 million, subject to closing adjustments, in the form of 125,000 shares of NW Natural common stock. Falls Water became a wholly-owned subsidiary of NWN Water and marked its first acquisition in the regulated water utility sector. This acquisition aligns with our water sector strategy as the acquisition provides NWN Water entry into Idaho, expands service area, and opens further opportunity for growth. Falls Water is based in Idaho Falls, Idaho and serves approximately 5,300 connections.

Through the purchase of all of the outstanding shares of Falls Water, NWN Water acquired the net assets and 100% control of Falls Water. We determined that the Falls Water acquisition met the criteria of a business combination, and as such performed a preliminary allocation of the consideration to the acquired assets and assumed liabilities based on their fair value as of the acquisition date, the majority of which was allocated to goodwill. The allocation is considered preliminary as we continue to evaluate working capital adjustments, certain tax positions, and goodwill. We do not expect any subsequent adjustments to be significant, and expect any such adjustments to be completed within the one-year measurement period. The acquisition costs were insignificant and were expensed as incurred. The results of Falls Water are not material to the consolidated financial results.

Preliminary goodwill of $6.6 million was recognized from this acquisition and is attributable to Falls Water's regulated service territory and experienced workforce as well as the strategic benefits expected from this high-growth service territory. NW Natural has included this goodwill in other for segment reporting purposes, and it is not deductible for income tax purposes. No intangible assets aside from goodwill were acquired.

We allocate goodwill to reporting units based on the expected benefit from the business combination. We perform an annual impairment assessment of goodwill at the reporting unit level, or more frequently if events and circumstances indicate that goodwill might be impaired. An impairment loss is recognized if the carrying value of a reporting unit’s goodwill exceeds its fair value.

An impairment analysis has not been performed in the current year, since all goodwill was acquired in the Falls Water acquisition, which closed in the third quarter of 2018. We anticipate that an annual impairment assessment of goodwill will occur in the fourth quarter of each year, beginning in the fourth quarter of 2018.