Northwest Natural Holding 10-Q 7 May 19 2019 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2019	Apr. 26, 2019
Document Information [Line Items]
Document Type	10-Q
Document Period End Date	Mar. 31, 2019
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Central Index Key	0001733998
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Registrant Name	NORTHWEST NATURAL HOLDING COMPANY
Entity Common Stock, Shares Outstanding		28,965,723
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Entity Small Business	false
Entity Emerging Growth Company	false
Northwest Natural Gas Company [Member]
Document Information [Line Items]
Document Type	10-Q
Document Period End Date	Mar. 31, 2019
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Central Index Key	0000073020
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Registrant Name	NORTHWEST NATURAL GAS COMPANY
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Entity Small Business	false
Entity Emerging Growth Company	false

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Operating revenues [Abstract]
Operating revenues	$ 285,348	$ 263,635
Operating expenses:
Cost of gas	105,457	108,106
Operations and maintenance	51,482	39,523
Environmental remediation	8,947	4,624
General taxes	9,027	9,474
Revenue taxes	11,926	12,429
Depreciation and amortization	21,572	20,875
Other operating expenses	892	853
Total operating expenses	209,303	195,884
Income from operations	76,045	67,751
Other income (expense), net	(13,747)	(834)
Interest expense, net	10,205	9,274
Income before income taxes	52,093	57,643
Income tax expense	8,675	15,632
Net income from continuing operations	43,418	42,011
Loss from discontinued operations, net of tax	(217)	(474)
Net income	43,201	41,537
Other comprehensive income:
Amortization of non-qualified employee benefit plan liability, net of taxes	115	154
Comprehensive income	$ 43,316	$ 41,691
Average common shares outstanding:
Basic (in shares)	28,906	28,753
Diluted (in shares)	28,970	28,803
Earnings from continuing operations per share of common stock:
Basic (in dollars per share)	$ 1.50	$ 1.46
Diluted (in dollars per share)	1.50	1.46
Earnings (loss) per share of common stock:
Basic (in dollars per share)	1.49	1.44
Diluted (in dollars per share)	$ 1.49	$ 1.44
Northwest Natural Gas Company [Member]
Operating revenues [Abstract]
Operating revenues	$ 284,846	$ 263,635
Operating expenses:
Cost of gas	105,513	108,164
Operations and maintenance	50,434	39,500
Environmental remediation	8,947	4,624
General taxes	8,988	9,459
Revenue taxes	11,926	12,429
Depreciation and amortization	21,504	20,868
Other operating expenses	890	853
Total operating expenses	208,202	195,897
Income from operations	76,644	67,738
Other income (expense), net	(13,768)	(815)
Interest expense, net	10,133	9,274
Income before income taxes	52,743	57,649
Income tax expense	8,848	15,635
Net income from continuing operations	43,895	42,014
Loss from discontinued operations, net of tax	0	(477)
Net income	43,895	41,537
Other comprehensive income:
Amortization of non-qualified employee benefit plan liability, net of taxes	115	154
Comprehensive income	$ 44,010	$ 41,691

Consolidated Statements of Co_2

Consolidated Statements of Comprehensive Income (Parentheticals) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Amortization of non-qualified employee benefit plan liability, tax	$ 41	$ 55
Northwest Natural Gas Company [Member]
Amortization of non-qualified employee benefit plan liability, tax	$ 41	$ 55

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Current assets:
Cash and cash equivalents	$ 12,817	$ 12,633	$ 11,215
Accounts receivable	93,617	66,970	77,897
Accrued unbilled revenue	36,147	57,827	38,752
Allowance for uncollectible accounts	(1,301)	(977)	(1,112)
Regulatory assets	46,317	41,930	45,900
Derivative instruments	7,890	9,001	1,130
Inventories	19,540	44,149	34,399
Gas reserves	16,157	16,647	15,124
Income Taxes Receivable, Current	6,000	6,000	0
Other current assets	20,293	28,472	16,877
Discontinued operations - current assets	14,632	13,269	1,512
Total current assets	272,109	295,921	241,694
Non-current assets:
Property, plant, and equipment	3,439,460	3,414,490	3,251,075
Less: Accumulated depreciation	1,005,117	993,118	972,773
Property, Plant and Equipment, Net	2,434,343	2,421,372	2,278,302
Gas reserves	61,907	66,197	80,560
Regulatory assets	327,194	371,786	343,037
Derivative instruments	541	725	1,148
Other investments	63,829	63,558	66,709
Operating lease right of use asset	6,163	0	0
Goodwill	8,954	8,954	0
Other non-current assets	16,077	14,149	7,030
Discontinued operations - non-current assets	0	0	10,859
Total non-current assets	2,919,008	2,946,741	2,787,645
Total assets	3,191,117	3,242,662	3,029,339
Current liabilities:
Short-term debt	176,391	217,620	50,000
Current maturities of long-term debt	104,158	29,989	74,785
Accounts payable	103,207	115,878	77,860
Taxes accrued	11,004	11,023	12,018
Interest accrued	9,233	7,306	9,262
Regulatory liabilities	46,770	47,436	34,946
Derivative instruments	2,845	12,381	17,607
Operating lease liabilities	4,656	0	0
Other current liabilities	54,543	54,492	39,166
Discontinued operations current liabilities	13,282	12,959	1,209
Total current liabilities	526,089	509,084	316,853
Long-term debt	632,484	706,247	683,497
Deferred credits and other non-current liabilities:
Deferred tax liabilities	293,662	280,463	283,129
Regulatory liabilities	600,698	611,560	600,442
Pension and other postretirement benefit liabilities	220,732	221,886	221,732
Derivative instruments	1,161	3,025	2,355
Operating lease liabilities	1,495	0	0
Other non-current liabilities	120,569	147,763	137,147
Discontinued operations non-current liabilities	0	0	11,979
Discontinued operations non-current liabilities			12,400
Total deferred credits and other non-current liabilities	1,238,317	1,264,697	1,256,784
Commitments and contingencies (see Note 16 and Note 17)
Equity:
Common stock	459,932	457,640	450,408
Retained earnings	342,734	312,182	330,081
Accumulated other comprehensive loss	(8,439)	(7,188)	(8,284)
Total equity	794,227	762,634	772,205
Total liabilities and equity	3,191,117	3,242,662	3,029,339
Northwest Natural Gas Company [Member]
Current assets:
Cash and cash equivalents	6,833	7,947	10,904
Accounts receivable	93,502	66,824	77,898
Accrued unbilled revenue	36,085	57,773	38,752
Receivables from affiliates	4,247	4,166	422
Allowance for uncollectible accounts	(1,300)	(975)	(1,113)
Regulatory assets	46,317	41,930	45,900
Derivative instruments	7,890	9,001	1,130
Inventories	19,528	44,126	34,399
Gas reserves	16,157	16,647	15,124
Other current assets	19,474	25,347	16,821
Discontinued operations - current assets	0	0	5,731
Total current assets	248,733	272,786	245,968
Non-current assets:
Property, plant, and equipment	3,435,304	3,410,439	3,250,700
Less: Accumulated depreciation	1,004,812	992,855	972,573
Property, Plant and Equipment, Net	2,430,492	2,417,584	2,278,127
Gas reserves	61,907	66,197	80,560
Regulatory assets	327,194	371,786	343,037
Derivative instruments	541	725	1,148
Other investments	50,212	49,922	53,018
Operating lease right of use asset	5,903	0	0
Other non-current assets	15,646	13,736	7,017
Discontinued operations - non-current assets	0	0	24,738
Total non-current assets	2,891,895	2,919,950	2,787,645
Total assets	3,140,628	3,192,736	3,033,613
Current liabilities:
Short-term debt	176,300	217,500	50,000
Current maturities of long-term debt	104,084	29,989	74,785
Accounts payable	102,232	114,937	77,590
Payables to affiliates	1,385	523	3,613
Taxes accrued	10,869	10,990	11,984
Interest accrued	9,225	7,273	9,262
Regulatory liabilities	46,770	47,436	34,946
Derivative instruments	2,845	12,381	17,607
Operating lease liabilities	4,477	0	0
Other current liabilities	53,155	53,027	39,180
Discontinued operations current liabilities	0	0	2,160
Total current liabilities	511,342	494,056	321,127
Long-term debt	630,370	704,134	683,497
Deferred credits and other non-current liabilities:
Deferred tax liabilities	307,704	294,739	299,526
Regulatory liabilities	600,698	611,560	600,442
Pension and other postretirement benefit liabilities	220,732	221,886	221,732
Derivative instruments	1,161	3,025	2,355
Operating lease liabilities	1,413	0	0
Other non-current liabilities	120,465	147,668	137,059
Discontinued operations non-current liabilities	0	0	4,330
Total deferred credits and other non-current liabilities	1,252,173	1,278,878	1,256,784
Equity:
Common stock	226,452	226,452	450,408
Retained earnings	528,730	496,404	330,081
Accumulated other comprehensive loss	(8,439)	(7,188)	(8,284)
Total equity	746,743	715,668	772,205
Total liabilities and equity	$ 3,140,628	$ 3,192,736	$ 3,033,613

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parentheticals) - $ / shares shares in Thousands, $ / shares in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Statement of Financial Position [Abstract]
Par Value (in dollars per share)	$ 0	$ 0	$ 0
Shares Authorized (in shares)	100,000	100,000	100,000
Shares outstanding (in shares)	28,962	28,880	28,781
Shares issued (in shares)	28,962	28,880	28,781

Consolidated Statement of Share

Consolidated Statement of Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock Including APIC [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Northwest Natural Gas Company [Member]	Northwest Natural Gas Company [Member]Common Stock Including APIC [Member]	Northwest Natural Gas Company [Member]Retained Earnings [Member]	Northwest Natural Gas Company [Member]Accumulated Other Comprehensive Income (Loss) [Member]
Beginning Balance at Dec. 31, 2017	$ 742,776	$ 448,865	$ 302,349	$ (8,438)	$ 742,776	$ 448,865	$ 302,349	$ (8,438)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	41,537		41,537		41,537		41,537
Other comprehensive income	41,691			154	41,691			154
Dividends on common stock			(13,805)				(13,805)
Stranded Deferred Tax Remeasurement Benefit	0
Stranded Deferred Tax Remeasurement Benefit | Accounting Standards Update 2018-02 [Member]			0	0			0	0
Stock-based compensation		1,172				1,172
Shares issued pursuant to equity based plans		371				371
Ending Balance at Mar. 31, 2018	$ 772,205	450,408	330,081	(8,284)	772,205	450,408	330,081	(8,284)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends per share of common stock	$ 0.4725
Beginning Balance at Dec. 31, 2018	$ 762,634	457,640	312,182	(7,188)	715,668	226,452	496,404	(7,188)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	43,201		43,201		43,895		43,895
Other comprehensive income	43,316			115	44,010			115
Dividends on common stock			(14,015)				(12,935)
Stranded Deferred Tax Remeasurement Benefit	1,366
Stranded Deferred Tax Remeasurement Benefit | Accounting Standards Update 2018-02 [Member]	1,400		1,400	(1,400)			1,400	(1,400)
Stock-based compensation		1,245				0
Shares issued pursuant to equity based plans		1,047				0
Ending Balance at Mar. 31, 2019	$ 794,227	$ 459,932	$ 342,734	$ (8,439)	$ 746,743	$ 226,452	$ 528,730	$ (8,439)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends per share of common stock	$ 0.4750

Consolidated Statement of Cash

Consolidated Statement of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Operating activities:
Net income	$ 43,201	$ 41,537
Adjustments to reconcile net income to cash provided by operations:
Depreciation and amortization	21,572	20,875
Regulatory amortization of gas reserves	4,780	4,073
Deferred income taxes	6,306	13,327
Qualified defined benefit pension plan expense	3,499	1,435
Contributions to qualified defined benefit pension plans	(1,490)	(1,720)
Deferred environmental expenditures, net	(3,685)	(1,280)
Amortization of environmental remediation	8,947	4,624
Regulatory revenue recovery deferral from the TCJA	450	6,424
Regulatory disallowance of pension costs	10,500	0
Other	3,171	879
Changes in assets and liabilities:
Receivables, net	(4,891)	10,552
Inventories	21,108	13,144
Income and other taxes	7,406	(6,865)
Accounts payable	(14,883)	(19,042)
Interest accrued	1,927	2,489
Deferred gas costs	(19,182)	3,519
Decoupling mechanism	7,903	5,431
Other, net	8,894	3,963
Discontinued operations	(739)	1,156
Cash provided by operating activities	104,794	104,521
Investing activities:
Capital expenditures	(48,764)	(57,329)
Other	(1,991)	(58)
Discontinued operations	(301)	(101)
Cash used in investing activities	(51,056)	(57,488)
Financing activities:
Proceeds from stock options exercised	1,546	0
Long-term debt retired	0	(22,000)
Change in short-term debt	(41,229)	(4,200)
Cash dividend payments on common stock	(12,935)	(12,781)
Other	(936)	(309)
Net Cash Provided by (Used in) Financing Activities	(53,554)	(39,290)
Increase in cash and cash equivalents	184	7,743
Cash and cash equivalents, beginning of period	12,633	3,472
Cash and cash equivalents, end of period	12,817	11,215
Supplemental disclosure of cash flow information:
Interest paid, net of capitalization	7,976	6,261
Income taxes paid (refunded), net	(90)	9,800
Northwest Natural Gas Company [Member]
Operating activities:
Net income	43,895	41,537
Adjustments to reconcile net income to cash provided by operations:
Depreciation and amortization	21,504	20,868
Regulatory amortization of gas reserves	4,780	4,073
Deferred income taxes	6,072	12,862
Qualified defined benefit pension plan expense	3,499	1,435
Contributions to qualified defined benefit pension plans	(1,490)	(1,720)
Deferred environmental expenditures, net	(3,685)	(1,280)
Amortization of environmental remediation	8,947	4,624
Regulatory revenue recovery deferral from the TCJA	450	6,424
Regulatory disallowance of pension costs	10,500	0
Other	3,117	854
Changes in assets and liabilities:
Receivables, net	(4,995)	10,552
Inventories	21,097	13,144
Income and other taxes	5,037	(6,860)
Accounts payable	(15,337)	(18,645)
Interest accrued	1,952	2,489
Deferred gas costs	(19,182)	3,519
Decoupling mechanism	7,903	5,431
Other, net	10,639	3,963
Discontinued operations	0	1,301
Cash provided by operating activities	104,703	104,571
Investing activities:
Capital expenditures	(48,658)	(57,329)
Other	(1,991)	(57)
Discontinued operations	0	(101)
Cash used in investing activities	(50,649)	(57,487)
Financing activities:
Long-term debt retired	0	(22,000)
Change in short-term debt	(41,200)	(4,200)
Cash dividend payments on common stock	(12,935)	(12,781)
Other	(1,033)	(309)
Net Cash Provided by (Used in) Financing Activities	(55,168)	(39,290)
Increase in cash and cash equivalents	(1,114)	7,794
Cash and cash equivalents, beginning of period	7,947	3,110
Cash and cash equivalents, end of period	6,833	10,904
Supplemental disclosure of cash flow information:
Interest paid, net of capitalization	7,889	6,261
Income taxes paid (refunded), net	$ (90)	$ 9,800

Organization and Principles of

Organization and Principles of Consolidation	3 Months Ended
	Mar. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Principles of Consolidation	ORGANIZATION AND PRINCIPLES OF CONSOLIDATION On October 1, 2018, we completed a reorganization into a holding company structure. In this reorganization, shareholders of NW Natural (the predecessor publicly held parent company) became shareholders of NW Holdings on a one-for-one basis; maintaining the same number of shares and ownership percentage as held in NW Natural immediately prior to the reorganization. NW Natural became a wholly-owned subsidiary of NW Holdings. Additionally, certain subsidiaries of NW Natural were transferred to NW Holdings. This reorganization was accounted for as a transaction among entities under common control. As required under accounting guidance, these subsidiaries are presented in this report as discontinued operations in the consolidated results of NW Natural. See Note 17 for additional information. The accompanying consolidated financial statements represent the respective, consolidated financial results of NW Holdings and NW Natural and all respective companies that each registrant directly or indirectly controls, either through majority ownership or otherwise. This is a combined report of NW Holdings and NW Natural, which includes separate consolidated financial statements for each registrant. NW Natural's regulated natural gas distribution activities are reported in the natural gas distribution (NGD) segment. The NGD segment is NW Natural's core operating business and serves residential, commercial, and industrial customers in Oregon and southwest Washington. The NGD segment is the only reportable segment for NW Holdings and NW Natural. All other activities, water businesses, and other investments are aggregated and reported as other at their respective registrant. In addition, NW Holdings has reported discontinued operations results related to the pending sale of Gill Ranch Storage, LLC (Gill Ranch). All prior period amounts have been retrospectively adjusted to reflect the change in reportable segments, the designation of Gill Ranch as a discontinued operation for NW Holdings, and the designation of subsidiaries previously owned by NW Natural that are now owned by NW Holdings as discontinued operations for NW Natural. These reclassifications and the reorganization activities described above had no effect on the prior year’s consolidated results of operations, financial condition, or cash flows. See Note 17 for additional information. NW Holdings' direct and indirect wholly-owned subsidiaries as of the filing date of this report include: • Northwest Natural Gas Company (NW Natural); • Northwest Energy Corporation (Energy Corp); • NWN Gas Reserves LLC (NWN Gas Reserves); • NW Natural Energy, LLC (NWN Energy); • NW Natural Gas Storage, LLC (NWN Gas Storage); ▪ Gill Ranch Storage, LLC (Gill Ranch), which is presented as a discontinued operation; • NNG Financial Corporation (NNG Financial); • KB Pipeline Company (KB); • NW Natural Water Company, LLC (NWN Water); ▪ Falls Water Co., Inc. (Falls Water); ▪ Salmon Valley Water Company; ▪ NW Natural Water of Oregon, LLC (NWN Water of Oregon); • Sunstone Water, LLC; ▪ NW Natural Water of Washington, LLC (NWN Water of Washington); • Cascadia Water, LLC (Cascadia); ▪ NW Natural Water of Idaho, LLC (NWN Water of Idaho); and • Gem State Water Company, LLC (Gem State) Investments in corporate joint ventures and partnerships that NW Holdings does not directly or indirectly control, and for which it is not the primary beneficiary, include NNG Financial's investment in Kelso-Beaver Pipeline and NWN Energy's investment in Trail West Holdings, LLC (TWH), which are accounted for under the equity method. NW Holdings and its direct and indirect subsidiaries are collectively referred to herein as NW Holdings, and NW Natural and its direct and indirect subsidiaries are collectively referred to herein as NW Natural. The consolidated financial statements of NW Holdings and NW Natural are presented after elimination of all intercompany balances and transactions. Information presented in these interim consolidated financial statements is unaudited, but includes all material adjustments management considers necessary for a fair statement of the results for each period reported including normal recurring accruals. These consolidated financial statements should be read in conjunction with the audited consolidated financial statements and related notes included in NW Holdings' and NW Natural's combined 2018 Annual Report on Form 10-K ( 2018 Form 10-K). A significant part of NW Natural's business is of a seasonal nature; therefore, NW Holdings and NW Natural results of operations for interim periods are not necessarily indicative of full year results. During the second quarter of 2018, we moved forward with our long-term strategic plans, which include a shift away from the California gas storage business. In June 2018, NWN Gas Storage, a wholly-owned subsidiary of NW Natural at the time and now a wholly-owned subsidiary of NW Holdings, entered into a Purchase and Sale Agreement that provides for the sale of all of the membership interests in its wholly-owned subsidiary, Gill Ranch, subject to various regulatory approvals and closing conditions. We have concluded that the pending sale of Gill Ranch qualifies as assets and liabilities held for sale and discontinued operations. As such, the results of Gill Ranch have been presented as a discontinued operation for NW Holdings for all periods presented and for NW Natural up until the holding company reorganization was effective on October 1, 2018 on the consolidated statements of comprehensive income and cash flows, and the assets and liabilities associated with Gill Ranch have been classified as discontinued operations assets and liabilities on the NW Holdings consolidated balance sheet. See Note 17 for additional information. Additionally, we reevaluated reportable segments and concluded that the remaining gas storage activities no longer meet the requirements to be separately reported as a segment. Interstate Storage Services is now reported in Other under NW Natural and NW Holdings as applicable, and all prior periods reflect this change. See Note 4 , which provides segment information. Notes to the consolidated financial statements reflect the activity of continuing operations for both NW Holdings and NW Natural for all periods presented, unless otherwise noted.

Significant Accounting Policies

Significant Accounting Policies	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Significant Accounting Policies	SIGNIFICANT ACCOUNTING POLICIES Significant accounting policies are described in Note 2 of the 2018 Form 10-K. There were no material changes to those accounting policies during the three months ended March 31, 2019 other than those set forth in this Note 2 . The following are current updates to certain critical accounting policy estimates and new accounting standards. Industry Regulation In applying regulatory accounting principles, NW Holdings and NW Natural capitalize or defer certain costs and revenues as regulatory assets and liabilities pursuant to orders of the Oregon Public Utilities Commission (OPUC), Washington Utilities and Transportation Commission (WUTC) or Idaho Public Utilities Commission (IPUC), which provide for the recovery of revenues or expenses from, or refunds to, utility customers in future periods, including a return or a carrying charge in certain cases. Amounts deferred as regulatory assets and liabilities were as follows: Regulatory Assets March 31, December 31, In thousands 2019 2018 2018 Current: Unrealized loss on derivatives (1) $ 2,845 $ 17,569 $ 12,381 Gas costs 17,927 591 2,873 Environmental costs (2) 5,090 5,818 5,601 Decoupling (3) 3,937 9,578 9,140 Pension balancing (4) 4,955 — — Income taxes 2,209 2,218 2,218 Other (5) 9,354 10,126 9,717 Total current $ 46,317 $ 45,900 $ 41,930 Non-current: Unrealized loss on derivatives (1) $ 1,161 $ 2,355 $ 3,025 Pension balancing (4) 50,408 63,940 74,173 Income taxes 17,758 19,267 19,185 Pension and other postretirement benefit liabilities 171,565 175,505 174,993 Environmental costs (2) 66,612 66,730 76,149 Gas costs 8,919 49 9,978 Decoupling (3) 250 2,663 2,545 Other (5) 10,521 12,528 11,738 Total non-current $ 327,194 $ 343,037 $ 371,786 Regulatory Liabilities March 31, December 31, In thousands 2019 2018 2018 Current: Gas costs $ 11,126 $ 17,798 $ 17,182 Unrealized gain on derivatives (1) 7,284 1,120 8,740 Decoupling (3) 2,055 2,501 2,264 Income taxes 7,763 — — Other (5) 18,542 13,527 19,250 Total current $ 46,770 $ 34,946 $ 47,436 Non-current: Gas costs $ 1,421 $ 5,639 $ 552 Unrealized gain on derivatives (1) 541 1,148 725 Decoupling (3) 614 1,253 — Income taxes (6) 202,692 219,795 225,408 Accrued asset removal costs (7) 384,702 365,363 380,464 Other (5) 10,728 7,244 4,411 Total non-current $ 600,698 $ 600,442 $ 611,560 (1) Unrealized gains or losses on derivatives are non-cash items and therefore do not earn a rate of return or a carrying charge. These amounts are recoverable through NGD rates as part of the annual Purchased Gas Adjustment (PGA) mechanism when realized at settlement. (2) Refer to footnote (3) of the Deferred Regulatory Asset table in Note 16 for a description of environmental costs. (3) This deferral represents the margin adjustment resulting from differences between actual and expected volumes. (4) Refer to Note 9 for information regarding the deferral of pension expenses. (5) Balances consist of deferrals and amortizations under approved regulatory mechanisms and typically earn a rate of return or carrying charge. (6) This balance represents estimated amounts associated with the Tax Cuts and Jobs Act. See Note 10 . (7) Estimated costs of removal on certain regulated properties are collected through rates. We believe all costs incurred and deferred at March 31, 2019 are prudent. All regulatory assets and liabilities are reviewed annually for recoverability, or more often if circumstances warrant. If we should determine that all or a portion of these regulatory assets or liabilities no longer meet the criteria for continued application of regulatory accounting, then NW Natural would be required to write-off the net unrecoverable balances in the period such determination is made. New Accounting Standards We consider the applicability and impact of all accounting standards updates (ASUs) issued by the Financial Accounting Standards Board (FASB). ASUs not listed below were assessed and determined to be either not applicable or are expected to have minimal impact on NW Natural's consolidated financial position or results of operations. Recently Adopted Accounting Pronouncements ACCUMULATED OTHER COMPREHENSIVE INCOME. On February 14, 2018, the FASB issued ASU 2018-02, "Income Statement—Reporting Comprehensive Income: Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income." This update was issued in response to concerns from certain stakeholders regarding the current requirements under U.S. GAAP that deferred tax assets and liabilities are adjusted for a change in tax laws or rates, and the effect is to be included in income from continuing operations in the period of the enactment date. This requirement is also applicable to items in accumulated other comprehensive income where the related tax effects were originally recognized in other comprehensive income. The adjustment of deferred taxes due to the new corporate income tax rate enacted through the Tax Cuts and Jobs Act (TCJA) on December 22, 2017 recognized in income from continuing operations causes the tax effects of items within accumulated other comprehensive income (referred to as stranded tax effects) to not reflect the appropriate tax rate. The amendments in this update allow but do not require a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the TCJA and require certain disclosures about stranded tax effects. NW Natural adopted and applied the standard in the first quarter of 2019. NW Natural elected to reclassify the stranded tax effects of the TJCA of $1.4 million from accumulated other comprehensive loss to retained earnings in the period of adoption. Going forward, our policy is that, in the event that regulation changes result in stranded tax effects, such amounts will be reclassified from accumulated other comprehensive income (loss) to retained earnings in the final period that the related deferred tax balance remeasurement is expected to impact income from continuing operations. DERIVATIVES AND HEDGING. On August 28, 2017, the FASB issued ASU 2017-12, "Derivatives and Hedging: Targeted Improvements to Accounting for Hedging Activities." The purpose of the amendment is to more closely align hedge accounting with companies’ risk management strategies. The ASU amends the accounting for risk component hedging, the hedged item in fair value hedges of interest rate risk, and amounts excluded from the assessment of hedge effectiveness. The guidance also amends the recognition and presentation of the effect of hedging instruments and includes other simplifications of hedge accounting. The amendments in this update were effective beginning January 1, 2019 and were applied prospectively to hedging instruments. The adoption did not have an impact on the financial statements or disclosures of NW Holdings or NW Natural. GOODWILL. On January 26, 2017, the FASB issued ASU 2017-04, "Simplifying the Test for Goodwill Impairment." The ASU removes Step 2 from the goodwill impairment test and under the amended guidance an entity should perform its annual goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount and recognize an impairment charge for the amount in which the carrying amounts exceed the fair value of the reporting unit. The amendments in this standard are effective for us beginning January 1, 2020 and early adoption is permitted for interim or annual goodwill impairment tests performed after January 1, 2017. NW Natural early adopted ASU 2017-04 in the quarter ended September 30, 2018. The adoption of this ASU did not materially affect the financial statements and disclosures of NW Holdings or NW Natural. LEASES. On February 25, 2016, the FASB issued ASU 2016-02, "Leases," which revises the existing lease accounting guidance. Pursuant to the new standard (“ASC 842”), lessees are required to recognize all leases, including operating leases that are greater than 12 months at lease commencement, on the balance sheet and record corresponding right of use assets and lease liabilities. Lessor accounting will remain substantially the same under the new standard. Quantitative and qualitative disclosures are also required for users of the financial statements to have a clear understanding of the nature of our leasing activities. We elected the alternative prospective transition approach for adoption beginning January 1, 2019. All comparative periods prior to January 1, 2019 will retain the financial reporting and disclosure requirements of ASC 840 “Leases” (“ASC 840”). There was no cumulative effect adjustment to the opening balance of retained earnings recorded as of January 1, 2019 for adoption as there were no initial direct costs or other capitalized costs related to the legacy leases that needed to be derecognized upon adoption of ASC 842. We elected the land easement optional practical expedient to not evaluate existing or expired land easements that were not previously accounted for as leases under the ASC 840 lease guidance. For the existing lease portfolio, we did not elect the optional practical expedient package to retain the legacy lease accounting conclusions upon adoption; we re-assessed our existing contracts under the new leasing standard including whether the contract meets the definition of a lease and lease classification. As a result, we determined that most of our underground gas storage contracts no longer meet the definition of a lease under the new lease standard. Our lease portfolio under the new standard consists primarily of our current leased headquarters, which expires in 2020. In October 2017, NW Natural entered into a 20-year operating lease agreement commencing in 2020 for a new headquarters location in Portland, Oregon. The lease was analyzed under ASC 840 in consideration of build-to-suit lease accounting guidance with the conclusion that NW Natural was the accounting owner of the asset during construction. Under the new lease standard, ASC 842, NW Natural is no longer considered the accounting owner of the asset during construction. As such, in January 2019 we derecognized the build-to-suit asset and liability balances of $26.0 million as of December 31, 2018 that were previously recorded within property, plant and equipment and other non-current liabilities in the consolidated balance sheet. Upon adoption on January 1, 2019, NW Holdings recorded an operating lease right of use asset and an associated operating lease liability of approximately $7.3 million , of which $7.0 million was recorded at NW Natural. Lease liabilities are measured using NW Natural's incremental borrowing rate based on information available at the lease commencement date in determining the present value of lease payments. See Note 6 . CLOUD COMPUTING. On August 29, 2018, the FASB issued ASU 2018-15, "Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract." The purpose of the amendment is to align the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. The amendments in this update are effective for us beginning January 1, 2020. Early adoption is permitted, and NW Holdings and NW Natural early adopted ASU 2018-15 in the quarter ended March 31, 2019 utilizing the prospective application methodology. The adoption of this ASU did not materially affect the financial statements and disclosures of NW Holdings or NW Natural. Recently Issued Accounting Pronouncements RETIREMENT BENEFITS. On August 28, 2018, the FASB issued ASU 2018-14, "Changes to the Disclosure Requirements for Defined Benefit Plans." The purpose of the amendment is to modify the disclosure requirements for defined benefit pension and other postretirement plans. The amendments in this update are effective for us beginning January 1, 2020. Early adoption is permitted. The amended presentation and disclosure guidance should be applied retrospectively. We are currently assessing the effect of this standard on disclosures. FAIR VALUE MEASUREMENT. On August 28, 2018, the FASB issued ASU 2018-13, "Changes to the Disclosure Requirements for Fair Value Measurement." The purpose of the amendment is to modify the disclosure requirements for fair value measurements. The amendments in this update are effective for us beginning January 1, 2020. Early adoption is permitted. The amendments on changes in unrealized gains and losses, the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements and the narrative description of measurement uncertainty should be applied prospectively. All other amendments should be applied retrospectively. We are currently assessing the effect of this standard on disclosures. CREDIT LOSSES. On June 16, 2016, the FASB issued ASU 2016-13, "Measurement of Credit Losses on Financial Instruments," which applies to financial assets subject to credit losses and measured at amortized cost. The new standard will require financial assets measured at amortized cost to be presented at the net amount expected to be collected and the allowance for credit losses is to be recorded as a valuation account that is deducted from the amortized cost basis. The amendments in this update are effective beginning January 1, 2020. Early adoption is permitted for fiscal years beginning after December 15, 2018. We are currently assessing the effect of this standard on our financial statements and disclosures.

Earnings Per Share

Earnings Per Share	3 Months Ended
	Mar. 31, 2019
Earnings Per Share [Abstract]
Earnings Per Share	EARNINGS PER SHARE Basic earnings per share are computed using NW Holdings' net income and the weighted average number of common shares outstanding for each period presented. Diluted earnings per share are computed in the same manner, except using the weighted average number of common shares outstanding plus the effects of the assumed exercise of stock options and the payment of estimated stock awards from other stock-based compensation plans that are outstanding at the end of each period presented. Antidilutive stock awards are excluded from the calculation of diluted earnings per common share. NW Holdings' diluted earnings or loss per share are calculated as follows: Three Months Ended March 31, In thousands, except per share data 2019 2018 Net Income from continuing operations $ 43,418 $ 42,011 Loss from discontinued operations, net of tax (217 ) (474 ) Net income $ 43,201 $ 41,537 Average common shares outstanding - basic 28,906 28,753 Additional shares for stock-based compensation plans (See Note 7) 64 50 Average common shares outstanding - diluted 28,970 28,803 Earnings from continuing operations per share of common stock: Basic $ 1.50 $ 1.46 Diluted $ 1.50 $ 1.46 Loss from discontinued operations per share of common stock: Basic $ (0.01 ) $ (0.02 ) Diluted $ (0.01 ) $ (0.02 ) Earnings per share of common stock: Basic $ 1.49 $ 1.44 Diluted $ 1.49 $ 1.44 Additional information: Antidilutive shares 5 16

Segment Information

Segment Information	3 Months Ended
	Mar. 31, 2019
Segment Reporting [Abstract]
Segment Information	SEGMENT INFORMATION We primarily operate in one reportable business segment, which is NW Natural's local gas distribution business and is referred to as the NGD s egment. During the second quarter of 2018, we moved forward with long-term strategic plans, which include a shift away from the California gas storage business, by entering into a Purchase and Sale Agreement that provides for the sale of all of the membership interests in Gill Ranch, subject to various regulatory approvals and closing conditions. As such, we reevaluated reportable segments and concluded that the remaining gas storage activities no longer meet the requirements of a reportable segment. Interstate Storage Services and asset management activities at the Mist gas storage facility, are now reported as other under NW Natural. NW Natural and NW Holdings also have investments and b usiness activities not specifically related to the NGD, which are aggregated and reported as other and described below for each entity. Natural Gas Distribution NW Natural's local gas distribution segment is a regulated utility principally engaged in the purchase, sale, and delivery of natural gas and related services to customers in Oregon and southwest Washington. In addition to NW Natural's local gas distribution business, the NGD segment also includes the portion of the Mist underground storage facility used to serve NGD customers, the North Mist gas storage expansion in Oregon, and NWN Gas Reserves, which is a wholly-owned subsidiary of Energy Corp. NW Natural NW Natural's activities in Other include Interstate Storage Services and third-party asset management services for the Mist facility in Oregon, appliance retail center operations, and corporate operating and non-operating revenues and expenses that cannot be allocated to NGD operations. Earnings from Interstate Storage Services assets are primarily related to firm storage capacity revenues. Earnings from the Mist facility also include revenue, net of amounts shared with NGD customers, from management of NGD assets at Mist and upstream pipeline capacity when not needed to serve NGD customers. Under the Oregon sharing mechanism, NW Natural retains 80% of the pre-tax income from these services when the costs of the capacity were not included in NGD rates, or 10% of the pre-tax income when the costs have been included in these rates. The remaining 20% and 90% , respectively, are recorded in a deferred regulatory account for crediting back to NGD customers. NW Holdings NW Holdings' activities in Other include all remaining activities not associated with NW Natural, specifically NWN Water, which consolidates the water operations and is pursuing other investments in the water sector itself and through its wholly-owned subsidiaries, NWN Gas Storage, a wholly-owned subsidiary of NWN Energy, NWN Energy's equity investment in TWH, which is pursuing development of a cross-Cascades transmission pipeline project (TWP), and other pipeline assets in NNG Financial. For more information on TWP, see Note 13 . Other also includes corporate revenues and expenses that cannot be allocated to other operations . All prior period amounts have been retrospectively adjusted to reflect the change in reportable segments and the designation of Gill Ranch as a discontinued operation for NW Holdings, and the designation of subsidiaries previously owned by NW Natural that are now owned by NW Holdings as discontinued operations for NW Natural. Segment Information Summary Inter-segment transactions were immaterial for the periods presented. The following table presents summary financial information concerning the reportable segments of continuing operations. See Note 17 for information regarding discontinued operations for NW Holdings and NW Natural. Three Months Ended March 31, In thousands NGD Other (NW Natural) NW Natural Other (NW Holdings) NW Holdings 2019 Operating revenues $ 279,041 $ 5,805 $ 284,846 $ 502 $ 285,348 Depreciation and amortization 21,249 255 21,504 68 21,572 Income (loss) from operations 72,898 3,746 76,644 (599 ) 76,045 Net income (loss) from continuing operations 41,206 2,689 43,895 (477 ) 43,418 Capital expenditures 48,606 52 48,658 106 48,764 Total assets at March 31, 2019 (1) 3,091,062 49,566 3,140,628 35,857 3,176,485 2018 Operating revenues $ 257,933 $ 5,702 $ 263,635 $ — $ 263,635 Depreciation and amortization 20,543 325 20,868 7 20,875 Income from operations 64,756 2,982 67,738 13 67,751 Net income (loss) from continuing operations 39,883 2,131 42,014 (3 ) 42,011 Capital expenditures 56,894 435 57,329 — 57,329 Total assets at March 31, 2018 (1) 2,952,294 50,850 3,003,144 13,824 3,016,968 Total assets at December 31, 2018 (1) 3,141,969 50,767 3,192,736 36,657 3,229,393 (1) Total assets for NW Holdings exclude assets related to discontinued operations of $14.6 million , $12.4 million , and $13.3 million as of March 31, 2019 , March 31, 2018 , and December 31, 2018 , respectively. Total assets for NW Natural exclude assets related to discontinued operations of $30.5 million as of March 31, 2018 . Natural Gas Distribution Margin NGD margin is a financial measure used by the Chief Operating Decision Maker (CODM) , consisting of NGD operating revenues, reduced by the associated cost of gas, environmental remediation expense, and revenue taxes. The cost of gas purchased for NGD customers is generally a pass-through cost in the amount of revenues billed to regulated NGD customers. Environmental remediation expense represents collections received from customers through the environmental recovery mechanism in Oregon as well as adjustments for the environmental earnings test. This is offset by environmental remediation expense presented in in operating expenses. Revenue taxes are collected from NGD customers and remitted to taxing authorities. The collections from customers are offset by the expense recognition of the obligation to the taxing authority. By subtracting cost of gas, environmental remediation expense, and revenue taxes from NGD operating revenues, NGD margin provides a key metric used by the CODM in assessing the performance of the NGD segment. The following table presents additional segment information concerning NGD margin: Three Months Ended March 31, In thousands 2019 2018 NGD margin calculation: NGD operating revenues $ 279,041 $ 257,933 Less: NGD cost of gas 105,513 108,164 Environmental remediation expense 8,947 4,624 Revenue taxes 11,926 12,429 NGD margin $ 152,655 $ 132,716

Leases (Notes)

Leases (Notes)	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
Leases of Lessee Disclosure	LEASES Lease Revenue Leasing revenue primarily consists of rental revenue for small leases of property owned by NW Natural to third parties. These transactions are accounted for as operating leases and the revenue is recognized on a straight-line basis over the term of the lease agreement. Our lessor portfolio also contains a sales-type lease for specialized compressor facilities to provide high pressure gas service. Lease payments are outlined in an OPUC-approved rate schedule over a 10-year term. There are no variable payments or residual value guarantees. The gain computed upon lease commencement was not significant. The components of lease revenue at NW Natural were as follows: In thousands Three months ended March 31, 2019 Lease revenue Operating leases $ 48 Sales-type leases 60 Total lease revenue $ 108 Total future minimum lease payments to be received under non-cancelable leases at NW Natural at March 31, 2019 are as follows: In thousands Operating Sales-Type Total 2019 (excluding the three months ended March 31, 2019) $ 94 $ 286 $ 380 2020 61 212 273 2021 49 198 247 2022 45 186 231 2023 45 173 218 Thereafter 138 478 616 Total lease revenue $ 432 $ 1,533 $ 1,965 Less: imputed interest 459 Total lease receivable $ 1,074 The total lease receivable above is reported under the NGD segment and included in “Other non-current assets” in the consolidated balance sheet. Additionally, under regulatory accounting, the imputed interest on the sales-type lease is recorded as depreciation expense on the consolidated statement of comprehensive income. North Mist Gas Storage Expansion Project In 2016, NW Natural began expanding its gas storage facility near Mist, Oregon to provide long-term, no-notice underground gas storage service to support gas-fired electric generating facilities that are intended to facilitate the integration of more wind power into the region's electric generation mix. This expansion project is in support of a local electric company’s gas-fired electric power generation facilities under an initial 30-year contract with options to extend, totaling up to an additional 50 years upon mutual agreement of the parties. When the expansion is placed into service during the spring of 2019, the investment will be accounted for as a sales-type lease with regulatory accounting deferral treatment. The investment will be included in rate base under an established tariff schedule already approved by the OPUC, with revenues recognized consistent with the schedule. Billing rates will be updated annually to the current depreciable asset level, forecasted operating expenses, and for differences between actual and expected costs incurred. Lease Expense Operating Leases We have operating leases for land, buildings and equipment. Our primary lease is for NW Natural's headquarters. Our leases have remaining lease terms of one year to 11 years . Many of our lease agreements include options to extend the lease, which we do not include in our minimum lease terms unless they are reasonably certain to be exercised. Short-term leases with a term of 12 months or less are not recorded on the balance sheet. As most of our leases do not provide an implicit rate and are entered into by NW Natural, we use NW Natural's incremental borrowing rate based on information available at the lease commencement date in determining the present value of lease payments. The components of lease expense, a portion of which is capitalized, were as follows: Three months ended March 31, 2019 In thousands NW Natural Other NW Holdings Operating lease expense $ 1,142 $ 46 $ 1,188 Short-term lease expense 160 — 160 Supplemental balance sheet information related to operating leases as of March 31, 2019 is as follows: In thousands NW Natural Other NW Holdings Operating lease right of use asset $ 5,903 $ 260 $ 6,163 Operating lease liabilities - current liabilities $ 4,477 $ 179 $ 4,656 Operating lease liabilities - non-current liabilities 1,413 82 1,495 Total operating lease liabilities $ 5,890 $ 261 $ 6,151 As of March 31, 2019 , the weighted average remaining lease term for the operating leases is 1.3 years for NW Natural. The weighted average discount rate used in the valuation of the operating lease right of use assets over the remaining lease term is 3.79% for NW Natural. Maturities of operating lease liabilities at March 31, 2019 were as follows: In thousands NW Natural Other NW Holdings 2019 (excluding the three months ended March 31, 2019) $ 3,462 $ 139 $ 3,601 2020 1,980 102 2,082 2021 101 28 129 2022 93 — 93 2023 71 — 71 Thereafter 497 — 497 Total lease payments 6,204 269 6,473 Less: imputed interest 314 8 322 Total lease obligations 5,890 261 6,151 Less: current obligations 4,477 179 4,656 Long-term lease obligations $ 1,413 $ 82 $ 1,495 Significant Lease Not Yet Commenced In October 2017, NW Natural entered into a 20 -year operating lease agreement for a new headquarters in Portland, Oregon in anticipation of the expiration of the current headquarters lease in 2020. The lease is expected to commence when construction of the asset is completed in late 2019 or early 2020. Total estimated base rent payments over the life of the lease are approximately $160 million . There is an option to extend the term of the lease for two additional seven -year periods. Cash Flow Information Supplemental cash flow information related to leases was as follows: Three months ended March 31, 2019 In thousands NW Natural Other NW Holdings Cash paid for amounts included in the measurement of lease liabilities Operating cash flows from operating leases $ 1,091 $ 43 $ 1,134 Right of use assets obtained in exchange for lease obligations Operating leases $ 6,987 $ 304 $ 7,291 Finance Leases NW Natural also leases building storage spaces for use as a gas meter room in order to provide natural gas to multifamily or mixed use developments. These contracts are accounted for as finance leases and typically involve a one-time upfront payment with no remaining liability. The right of use asset for finance leases was $0.2 million at March 31, 2019 . Lease Disclosures Related to Periods Prior to the First Quarter of 2019 Land, buildings, and equipment are leased under agreements that expire in various years, including a 99-year land lease that extends through 2108. Rental costs for continuing operations were $5.9 million , $7.3 million , and $5.9 million for the years ended December 31, 2018 , 2017 , and 2016 , respectively, a portion of which was capitalized. The following table reflects NW Natural's future minimum lease payments due under non-cancelable operating leases for continuing operations at December 31, 2018 . These commitments relate principally to the lease of the office headquarters and underground gas storage facilities. In thousands Minimum lease payments 2019 $ 5,368 2020 4,812 2021 7,077 2022 7,223 2023 7,304 Thereafter 149,881 Total $ 181,665

Revenue (Notes)

Revenue (Notes)	3 Months Ended
	Mar. 31, 2019
Revenue from Contract with Customer [Abstract]
Revenue from Contract with Customer	REVENUE The following table presents disaggregated revenue from continuing operations: Three Months Ended March 31, In thousands NGD Other (NW Natural) NW Natural Other (NW Holdings) NW Holdings 2019 Natural gas sales $ 296,186 $ — $ 296,186 $ — $ 296,186 Gas storage revenue, net — 2,783 2,783 — 2,783 Asset management revenue, net — 1,506 1,506 — 1,506 Appliance retail center revenue — 1,516 1,516 — 1,516 Other revenue — — — 502 502 Revenue from contracts with customers 296,186 5,805 301,991 502 302,493 Alternative revenue (17,253 ) — (17,253 ) — (17,253 ) Leasing revenue 108 — 108 — 108 Total operating revenues $ 279,041 $ 5,805 $ 284,846 $ 502 $ 285,348 2018 Natural gas sales $ 258,229 $ — $ 258,229 $ — $ 258,229 Gas storage revenue, net — 2,577 2,577 — 2,577 Asset management revenue, net — 1,579 1,579 — 1,579 Appliance retail center revenue — 1,546 1,546 — 1,546 Other revenue — — — — — Revenue from contracts with customers 258,229 5,702 263,931 — 263,931 Alternative revenue (372 ) — (372 ) — (372 ) Leasing revenue 76 — 76 — 76 Total operating revenues $ 257,933 $ 5,702 $ 263,635 $ — $ 263,635 NW Natural's revenue represents substantially all of NW Holdings' revenue and is recognized for both registrants when the obligation to customers is satisfied and in the amount expected to be received in exchange for transferring goods or providing services. Revenue from contracts with customers contains one performance obligation that is generally satisfied over time, using the output method based on time elapsed, due to the continuous nature of the service provided. The transaction price is determined by a set price agreed upon in the contract or dependent on regulatory tariffs. Customer accounts are settled on a monthly basis or paid at time of sale and based on historical experience. It is probable that we will collect substantially all of the consideration to which we are entitled. NW Holdings and NW Natural do not have any material contract assets, as net accounts receivable and accrued unbilled revenue balances are unconditional and only involve the passage of time until such balances are billed and collected. NW Holdings and NW Natural do not have any material contract liabilities. Revenue-based taxes are primarily franchise taxes, which are collected from NGD customers and remitted to taxing authorities. Beginning January 1, 2018, revenue taxes are included in operating revenues with an equal and offsetting expense recognized in operating expenses in the consolidated statements of comprehensive income. Natural Gas Distribution Natural gas sales. NW Natural's primary source of revenue is providing natural gas to customers in the NGD service territory, which includes residential, commercial, industrial and transportation customers. NGD revenue is generally recognized over time upon delivery of the gas commodity or service to the customer, and the amount of consideration received and recognized as revenue is dependent on the Oregon and Washington tariffs. Customer accounts are to be paid in full each month, and there is no right of return or warranty for services provided. Revenues include firm and interruptible sales and transportation services, franchise taxes recovered from the customer, late payment fees, service fees, and accruals for gas delivered but not yet billed (accrued unbilled revenue). The accrued unbilled revenue balance is based on estimates of deliveries during the period from the last meter reading and management judgment is required for a number of factors used in this calculation, including customer use and weather factors. We applied the significant financing practical expedient and have not adjusted the consideration NW Natural expects to receive from NGD customers for the effects of a significant financing component as all payment arrangements are settled annually. Due to the election of the right to invoice practical expedient, we do not disclose the value of unsatisfied performance obligations as of March 31, 2019 . Alternative revenue. Weather normalization (WARM) and decoupling mechanisms are considered to be alternative revenue programs. Alternative revenue programs are considered to be contracts between NW Natural and its regulator and are excluded from revenue from contracts with customers. Leasing revenue. Leasing revenue primarily consists of rental revenue for small leases of property owned by NW Natural to third parties. The majority of the transactions are accounted for as operating leases and the revenue is recognized on a straight-line basis over the term of the lease agreement. Lease revenue is excluded from revenue from contracts with customers. See Note 6 . NW Natural Other Gas storage revenue. NW Natural's other revenue includes gas storage activity, which includes Interstate Storage Services used to store natural gas for customers. Gas storage revenue is generally recognized over time as the gas storage service is provided to the customer and the amount of consideration received and recognized as revenue is dependent on set rates defined per the storage agreements. Noncash consideration in the form of dekatherms of natural gas is received as consideration for providing gas injection services to gas storage customers. This noncash consideration is measured at fair value using the average spot rate. Customer accounts are generally paid in full each month, and there is no right of return or warranty for services provided. Revenues include firm and interruptible storage services, net of the profit sharing amount refunded to NGD customers. Asset management revenue. Asset management revenue is generally recognized over time using a straight-line approach over the term of each contract, and the amount of consideration received and recognized as revenue is dependent on a variable pricing model. Variable revenues earned above guaranteed amounts are estimated and recognized at the end of each period using the most likely amount approach. Revenues include management services of the storage assets and pipeline capacity provided, net of the profit sharing amount refunded to NGD customers. Asset management accounts are settled on a monthly basis. As of March 31, 2019 , unrecognized revenue for the fixed component of the transaction price related to gas storage and asset management revenue was approximately $52.2 million . Of this amount, approximately $10.2 million will be recognized during the remainder of 2019 , $11.7 million in 2020 , $10.7 million in 2021 , $7.0 million in 2022 , $5.8 million in 2023 and $6.8 million thereafter. The amounts presented here are calculated using current contracted rates. Appliance retail center revenue. NW Natural owns and operates an appliance store that is open to the public, where customers can purchase natural gas home appliances. Revenue from the sale of appliances is recognized at the point in time in which the appliance is transferred to the third party responsible for delivery and installation services and when the customer has legal title to the appliance. It is required that the sale be paid for in full prior to transfer of legal title. The amount of consideration received and recognized as revenue varies with changes in marketing incentives and discounts offered to customers. NW Holdings Other NW Holdings' primary source of other revenue is providing water distribution services to customers. Water distribution revenue is generally recognized over time upon delivery of the water commodity or service to the customer, and the amount of consideration received and recognized as revenue is dependent on the Oregon, Washington and Idaho tariffs. Customer accounts are to be paid in full each month, and there is no right of return or warranty for services provided. We applied the significant financing practical expedient and have not adjusted the consideration we expect to receive from water distribution customers for the effects of a significant financing component as all payment arrangements are settled annually. Due to the election of the right to invoice practical expedient, we do not disclose the value of unsatisfied performance obligations as of March 31, 2019 .

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2019
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	STOCK-BASED COMPENSATION Stock-based compensation plans are designed to promote stock ownership in NW Holdings by employees and officers. These compensation plans include a Long Term Incentive Plan (LTIP), an Employee Stock Purchase Plan (ESPP), and a Restated Stock Option Plan. For additional information on stock-based compensation plans, see Note 7 in the 2018 Form 10-K and the updates provided below. Long Term Incentive Plan Performance Shares LTIP performance shares incorporate a combination of market, performance, and service-based factors. During the three months ended March 31, 2019 , no performance-based shares were granted under the LTIP for accounting purposes. In February 2019 and 2018, 2019 and 2018 LTIP shares were awarded to participants; however, the agreements allow for one of the performance factors to remain variable until the first quarter of the third year of the award period. As the performance factor will not be approved until the first quarters of 2021 and 2020, respectively, there is not a mutual understanding of the awards' key terms and conditions between NW Holdings and the participants as of March 31, 2019 , and therefore, no expense was recognized for the 2019 and 2018 awards. NW Holdings will calculate the grant date fair value and NW Natural and other subsidiaries will recognize expense over the remaining service period for each award once the final performance factor has been approved. For the 2019 and 2018 LTIP awards, share payouts range from a threshold of 0% to a maximum of 200% based on achievement of pre-established goals. The performance criteria for the 2019 and 2018 performance shares consists of a three-year Return on Invested Capital (ROIC) threshold that must be satisfied and a cumulative EPS factor, which can be modified by a total shareholder return factor (TSR modifier) relative to the performance of the Russell 2500 Utilities Index over the three -year performance period of each respective award. If the targets were achieved for the 2019 and 2018 awards, NW Holdings would grant 36,250 and 33,163 shares in the first quarters of 2021 and 2020, respectively. As of March 31, 2019 , there was $0.8 million of unrecognized compensation cost associated with the 2017 LTIP grants, which is expected to be recognized through 2019 . Restricted Stock Units During the three months ended March 31, 2019 , 28,884 RSUs were granted under the LTIP with a weighted-average grant date fair value of $64.26 per share. Generally, the RSUs awarded are forfeitable and include a performance-based threshold as well as a vesting period of four years from the grant date. Generally, an RSU obligates NW Holdings, upon vesting, to issue the RSU holder one share of common stock plus a cash payment equal to the total amount of dividends paid per share between the grant date and vesting date of that portion of the RSU. The fair value of an RSU is equal to the closing market price of common stock on the grant date. As of March 31, 2019 , there was $ 4.0 million of unrecognized compensation cost from grants of RSUs, which is expected to be recognized by NW Natural and other subsidiaries over a period extending through 2023 .

Debt

Debt	3 Months Ended
	Mar. 31, 2019
Debt Disclosure [Abstract]
Debt	DEBT Short-Term Debt At March 31, 2019 , NW Holdings had short-term debt outstanding of $176.4 million , substantially all of which was recorded at NW Natural and was comprised primarily of NW Natural's commercial paper. The carrying cost of commercial paper approximates fair value using Level 2 inputs. See Note 2 in the 2018 Form 10-K for a description of the fair value hierarchy. At March 31, 2019 , NW Natural's commercial paper had a maximum remaining maturity of 33 days and average remaining maturity of 17 days. Long-Term Debt At March 31, 2019 , NW Holdings had long-term debt outstanding of $736.6 million , substantially all of which was recorded at NW Natural and included $5.2 million of unamortized debt issuance costs. NW Natural's long-term debt consists of first mortgage bonds (FMBs) with maturity dates ranging from 2019 through 2048 , interest rates ranging from 2.822% to 9.050% , and a weighted average coupon rate of 5.009% . Fair Value of Long-Term Debt NW Holdings' and NW Natural's outstanding debt does not trade in active markets. The fair value of long-term debt is estimated using the value of outstanding debt at natural gas distribution companies with similar credit ratings, terms, and remaining maturities to NW Holdings' and NW Natural's debt that actively trade in public markets. Substantially all outstanding debt at NW Holdings is comprised of NW Natural debt. These valuations are based on Level 2 inputs as defined in the fair value hierarchy. See Note 2 in the 2018 Form 10-K for a description of the fair value hierarchy. The following table provides an estimate of the fair value of NW Natural's long-term debt, including current maturities of long-term debt, using market prices in effect on the valuation date: March 31, December 31, In thousands 2019 2018 2018 Gross long-term debt $ 739,700 $ 764,700 $ 739,700 Unamortized debt issuance costs (5,246 ) (6,418 ) (5,577 ) Carrying amount $ 734,454 $ 758,282 $ 734,123 Estimated fair value (1) $ 775,590 $ 807,288 $ 760,222 (1) Estimated fair value does not include unamortized debt issuance costs.

Pension and Other Postretiremen

Pension and Other Postretirement Benefit Costs	3 Months Ended
	Mar. 31, 2019
Pension and Other Postretirement Benefits Cost (Reversal of Cost) [Abstract]
Pension and Other Postretirement Benefit Costs	PENSION AND OTHER POSTRETIREMENT BENEFIT COSTS The service cost component of net periodic benefit cost for NW Natural pension and other postretirement benefit plans is recognized in operations and maintenance expense in the consolidated statements of comprehensive income. The other non-service cost components are recognized in other income (expense), net in the consolidated statements of comprehensive income. The following table provides the components of net periodic benefit cost for the pension and other postretirement benefit plans: Three Months Ended March 31, Pension Benefits Other Postretirement Benefits In thousands 2019 2018 2019 2018 Service cost $ 1,517 $ 1,807 $ 68 $ 80 Interest cost 4,662 4,183 281 241 Expected return on plan assets (5,207 ) (5,151 ) — — Amortization of prior service costs 2 11 (117 ) (117 ) Amortization of net actuarial loss 3,603 4,523 97 110 Net periodic benefit cost 4,577 5,373 329 314 Amount allocated to construction (586 ) (682 ) (24 ) (27 ) Amount deferred to regulatory balancing account — (2,756 ) — — Net periodic benefit cost charged to expense 3,991 1,935 305 287 Regulatory pension disallowance 10,500 — — — Amortization of regulatory balancing account 12,511 — — — Net amount charged to expense $ 27,002 $ 1,935 $ 305 $ 287 The service cost component of net periodic benefit costs is reduced by amounts capitalized to NGD plant based on approximately 25% to 35% payroll overhead charge. In addition, a certain amount of net periodic benefit costs were recorded to the regulatory balancing account, representing net periodic pension expense for the qualified plan above the amount set in rates, as approved by the OPUC, from 2011 through October 31, 2018. In March 2019, the OPUC issued an order concluding the NW Natural 2018 Oregon rate case which allowed for the application of certain deferred revenues and tax benefits from the TCJA against NW Natural's pension regulatory balancing account. A corresponding total of $12.5 million in pension expenses were recognized in operating and maintenance expense and other income (expense), net in the consolidated statements of comprehensive income, with offsetting benefits recorded within operating revenues and income taxes. The Order also directed NW Natural to reduce the balancing account by an additional $10.5 million , which was also charged to operating and maintenance expense and other income (expense), net in the consolidated statements of comprehensive income. The following table presents amounts recognized in accumulated other comprehensive loss (AOCL) and the changes in AOCL related to non-qualified employee benefit plans: Three Months Ended March 31, In thousands 2019 2018 Beginning balance $ (7,188 ) $ (8,438 ) Amounts reclassified from AOCL: Amortization of actuarial losses 156 209 Reclassification of stranded tax effects (1) (1,366 ) — Total reclassifications before tax (1,210 ) 209 Tax (benefit) expense (41 ) (55 ) Total reclassifications for the period (1,251 ) 154 Ending balance $ (8,439 ) $ (8,284 ) (1) Reclassification of $1.4 million of income tax effects resulting from the TCJA from accumulated other comprehensive loss to retained earnings was made pursuant to the adoption of ASU 2018-02. See Note 2 . Employer Contributions to Company-Sponsored Defined Benefit Pension Plans For the three months ended March 31, 2019 , NW Natural made cash contributions totaling $1.5 million to qualified defined benefit pension plans. NW Natural expects further plan contributions of $9.5 million during the remainder of 2019 . Defined Contribution Plan The Retirement K Savings Plan is a qualified defined contribution plan under Internal Revenue Code Sections 401(a) and 401(k). Employer contributions totaled $2.1 million and $2.0 million for the three months ended March 31, 2019 and 2018 , respectively. See Note 9 in the 2018 Form 10-K for more information concerning these retirement and other postretirement benefit plans.

Income Tax

Income Tax	3 Months Ended
	Mar. 31, 2019
Income Tax Disclosure [Abstract]
Income Tax	INCOME TAX An estimate of annual income tax expense is made each interim period using estimates for annual pre-tax income, regulatory flow-through adjustments, tax credits, and other items. The estimated annual effective tax rate is applied to year-to-date, pre-tax income to determine income tax expense for the interim period consistent with the annual estimate. Discrete events are recorded in the interim period in which they occur or become known. The effective income tax rate varied from the combined federal and state statutory tax rates due to the following: Three Months Ended March 31, NW Holdings NW Natural Dollars in thousands 2019 2018 2019 2018 Income taxes at statutory rates (federal and state) $ 14,313 $ 15,368 $ 14,485 $ 15,372 Increase (decrease): Differences required to be flowed-through by regulatory commissions (5,260 ) 849 (5,260 ) 849 Other, net (378 ) (585 ) (377 ) (586 ) Total provision for income taxes on continuing operations $ 8,675 $ 15,632 $ 8,848 $ 15,635 Effective tax rate for continuing operations 16.7 % 27.1 % 16.8 % 27.1 % The NW Holdings and NW Natural effective income tax rate for the three months ended March 31, 2019 compared to the same period in 2018 changed primarily as a result of regulatory amortization of deferred TCJA benefits as approved in the March 2019 OPUC order. See "U.S. Federal TCJA Matters" below and Note 10 in the 2018 Form 10-K for more detail on income taxes and effective tax rates. The IRS Compliance Assurance Process (CAP) examination of the 2017 tax year was completed during the first quarter of 2019. There were no material changes to the return as filed. The 2018 tax year is subject to examination under CAP and the 2019 tax year CAP application has been accepted by the IRS. The Oregon State examination of tax years 2015, 2016, and 2017 was completed in January 2019. There were no material changes to the returns as originally filed. U.S. Federal TCJA Matters On December 22, 2017, the TCJA was enacted and permanently lowered the U.S. federal corporate income tax rate to 21% from the previous maximum rate of 35% , effective for the tax year beginning January 1, 2018. The TCJA included specific provisions related to regulated public utilities that provide for the continued deductibility of interest expense and the elimination of bonus tax depreciation for property both acquired and placed into service on or after January 1, 2018. See Note 10 in the 2018 Form 10-K. NW Natural previously filed applications with the OPUC and WUTC to defer the NGD net income tax benefits resulting from the TCJA. In March 2019, the OPUC issued an order addressing the regulatory amortization of the income tax benefits from the TCJA that NW Natural deferred for Oregon customers in December of 2017. Under the order, NW Natural will provide the benefit of these TCJA income tax deferrals to Oregon customers through ongoing annual credits to customer base rates and as a one-time recovery of a portion of the pension balancing account regulatory asset balance. On an annualized basis, it is anticipated that the income tax benefits from the provision of these TCJA benefits to customers should approximate the reduction to pretax income that occurs as a result of the customer base rate credits and one-time recovery of a portion of the pension balancing account. The resolution of deferred TCJA income tax benefits for Washington customers is expected later this year as part of NW Natural's Washington general rate case.

Property, Plant and Equipment (

Property, Plant and Equipment (Notes)	3 Months Ended
	Mar. 31, 2019
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment Disclosure [Text Block]	PROPERTY, PLANT, AND EQUIPMENT The following table sets forth the major classifications of property, plant, and equipment and accumulated depreciation of continuing operations: March 31, December 31, In thousands 2019 2018 2018 NW Natural: NGD plant in service $ 3,159,754 $ 3,003,962 $ 3,134,122 NGD work in progress 204,938 177,133 204,978 Less: Accumulated depreciation 985,961 954,858 974,252 NGD plant, net 2,378,731 2,226,237 2,364,848 Other plant in service 65,283 65,353 66,009 Other construction work in progress 5,329 4,252 5,330 Less: Accumulated depreciation 18,851 17,715 18,603 Other plant, net (1) 51,761 51,890 52,736 Total property, plant, and equipment $ 2,430,492 $ 2,278,127 $ 2,417,584 Other (NW Holdings): Other plant in service $ 4,156 $ 375 $ 4,051 Less: Accumulated depreciation 305 200 263 Other plant, net (1) $ 3,851 $ 175 $ 3,788 NW Holdings: Total property, plant, and equipment $ 2,434,343 $ 2,278,302 $ 2,421,372 NW Natural and NW Holdings: Capital expenditures in accrued liabilities $ 25,035 $ 21,855 $ 23,676 (1) NW Natural p reviously reported other balances were restated due to certain assets and liabilities now being classified as discontinued operations assets and liabilities in its balance sheets. See Note 17 for further discussion. NW Holdings Other plant balances include long-lived assets associated with water operations and non-regulated activities not held by NW Natural or its subsidiaries. NW Natural Other plant balances include long-lived assets not related to NGD. In October 2017, NW Natural entered into a 20 -year operating lease agreement commencing in 2020 for its new headquarters location in Portland, Oregon. Under the new lease standard, NW Natural is no longer considered the accounting owner of the asset during construction. As such, the build to suit asset and liability balances at December 31, 2018 of $26.0 million were derecognized in January 2019. The previous build to suit balances were recorded under ASC 840 within property, plant and equipment and other non-current liabilities in the consolidated balance sheet. See Note 16 in the 2018 Form 10-K.

Gas Reserves

Gas Reserves	3 Months Ended
	Mar. 31, 2019
Gas Reserves [Abstract]
Gas Reserves	GAS RESERVES NW Natural has invested $188 million through the gas reserves program in the Jonah Field located in Wyoming as of March 31, 2019 . Gas reserves are stated at cost, net of regulatory amortization, with the associated deferred tax benefits recorded as liabilities in the consolidated balance sheets. The investment in gas reserves provides long-term price protection for NGD customers through the original agreement with Encana Oil & Gas (USA) Inc. under which NW Natural invested $178 million and the amended agreement with Jonah Energy LLC under which an additional $10 million was invested. The cost of gas, including a carrying cost for the rate base investment, is included in the annual Oregon PGA filing, which allows NW Natural to recover these costs through customer rates. The investment under the original agreement, less accumulated amortization and deferred taxes, earns a rate of return. See Note 12 in the 2018 Form 10-K. Gas produced from the additional wells is included in the Oregon PGA at a fixed rate of $0.4725 per therm, which approximates the 10 -year hedge rate plus financing costs at the inception of the investment. The following table outlines NW Natural's net gas reserves investment: March 31, December 31, In thousands 2019 2018 2018 Gas reserves, current $ 16,157 $ 15,124 $ 16,647 Gas reserves, non-current 171,150 172,412 170,660 Less: Accumulated amortization 109,243 91,852 104,463 Total gas reserves (1) 78,064 95,684 82,844 Less: Deferred taxes on gas reserves 19,638 22,115 20,071 Net investment in gas reserves $ 58,426 $ 73,569 $ 62,773 (1) The net investment in additional wells included in total gas reserves was $ 4.5 million , $ 5.6 million and $ 4.8 million at March 31, 2019 and 2018 and December 31, 2018 , respectively. NW Natural's investment is included in NW Holdings' and NW Natural's consolidated balance sheets under gas reserves with the maximum loss exposure limited to the investment balance.

Investments

Investments	3 Months Ended
	Mar. 31, 2019
Investments [Abstract]
Investments	INVESTMENTS Investments in Gas Pipeline Trail West Pipeline, LLC (TWP), a wholly-owned subsidiary of TWH, is pursuing the development of a new gas transmission pipeline that would provide an interconnection with NW Natural's NGD system. NWN Energy, a wholly-owned subsidiary of NW Holdings, owns 50% of TWH, and 50% is owned by TransCanada American Investments Ltd., an indirect wholly-owned subsidiary of TransCanada Corporation. Variable Interest Entity (VIE) Analysis TWH is a VIE, with NW Holdings' investment in TWP reported under equity method accounting. It has been determined that NW Holdings is not the primary beneficiary of TWH’s activities as it only has a 50% share of the entity, and there are no stipulations that allow NW Holdings a disproportionate influence over it. Investments in TWH and TWP are included in other investments in NW Holdings' balance sheet. If this investment is not developed, then the maximum loss exposure related to TWH is limited to NW Holdings' equity investment balance, less its share of any cash or other assets available to NW Holdings as a 50% owner. The investment balance in TWH was $13.4 million at March 31, 2019 and 2018 and December 31, 2018 . See Note 13 in the 2018 Form 10-K. Other Investments Other investments include financial investments in life insurance policies, which are accounted for at cash surrender value, net of policy loans. See Note 13 in the 2018 Form 10-K.

Business Combinations Business

Business Combinations Business Combinations	3 Months Ended
	Mar. 31, 2019
Business Combinations [Abstract]
Business Combination Disclosure [Text Block]	BUSINESS COMBINATIONS There were no business combinations completed in the first quarter of 2019. 2018 Business Combinations Falls Water On September 13, 2018 , NWN Water, then a wholly-owned subsidiary of NW Natural and now a wholly-owned subsidiary of NW Holdings, completed the acquisition of Falls Water Co., Inc. (Falls Water), 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 water utility sector. This acquisition aligns with NW Holdings' 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 of December 31, 2018, and is primarily associated with certain tax positions and goodwill. Subsequent adjustments are not expected to be significant, and any such adjustments are expected to be completed within a 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 of NW Holdings. Preliminary goodwill of $6.4 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 Holdings 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. Other Acquisitions During 2018, in addition to the Falls Water acquisition, NWN Water completed three acquisitions qualifying as business combinations. The aggregate fair value of the preliminary consideration transferred for these acquisitions was approximately $2.8 million . These business combinations, both individually and in aggregate, were not significant to NW Holdings' results of operations. Goodwill 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. As a result of all acquisitions completed in 2018, total goodwill was $9.0 million as of March 31, 2019 and December 31, 2018 . The annual impairment assessment of goodwill occurs in the fourth quarter of each year. There have been no impairments recognized to date.

Derivative Instruments

Derivative Instruments	3 Months Ended
	Mar. 31, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments	DERIVATIVE INSTRUMENTS NW Natural enters into financial derivative contracts to hedge a portion of the NGD segment's natural gas sales requirements. These contracts include swaps, options and combinations of option contracts. These derivative financial instruments are primarily used to manage commodity price variability. A small portion of NW Natural's derivative hedging strategy involves foreign currency exchange contracts. NW Natural enters into these financial derivatives, up to prescribed limits, primarily to hedge price variability related to physical gas supply contracts as well as to hedge spot purchases of natural gas. The foreign currency forward contracts are used to hedge the fluctuation in foreign currency exchange rates for pipeline demand charges paid in Canadian dollars. In the normal course of business, NW Natural also enters into indexed-price physical forward natural gas commodity purchase contracts and options to meet the requirements of NGD customers. These contracts qualify for regulatory deferral accounting treatment. NW Natural also enters into exchange contracts related to the third-party asset management of its gas portfolio, some of which are derivatives that do not qualify for hedge accounting or regulatory deferral, but are subject to NW Natural's regulatory sharing agreement. These derivatives are recognized in operating revenues, net of amounts shared with NGD customers. Notional Amounts The following table presents the absolute notional amounts related to open positions on NW Natural derivative instruments: March 31, December 31, In thousands 2019 2018 2018 Natural gas (in therms): Financial 255,550 326,080 408,850 Physical 422,825 420,200 472,275 Foreign exchange $ 7,241 $ 7,611 $ 6,936 Purchased Gas Adjustment (PGA) Derivatives entered into by NW Natural for the procurement or hedging of natural gas for future gas years generally receive regulatory deferral accounting treatment. In general, commodity hedging for the current gas year is completed prior to the start of the gas year, and hedge prices are reflected in weighted-average cost of gas in the PGA filing. Hedge contracts entered into after the start of the PGA period are subject to the PGA incentive sharing mechanism in Oregon. NW Natural entered the 2018-19 and 2017-18 gas year with forecasted sales volumes hedged at 48% and 49% in financial swap and option contracts, and 24% and 26% in physical gas supplies, respectively. Hedge contracts entered into prior to the PGA filing in September 2018 were included in the PGA for the 2018-19 gas year. Hedge contracts entered into after the PGA filing, and related to subsequent gas years, may be included in future PGA filings and qualify for regulatory deferral. Unrealized and Realized Gain/Loss The following table reflects the income statement presentation for the unrealized gains and losses from NW Natural's derivative instruments, which also represents all derivative instruments at NW Holdings: Three Months Ended March 31, 2019 2018 In thousands Natural gas commodity Foreign exchange Natural gas commodity Foreign exchange Benefit (expense) to cost of gas $ 7,007 $ (89 ) $ (5,747 ) $ (154 ) Operating revenues (expense) 2,367 — (227 ) — Amounts deferred to regulatory accounts on balance sheet (9,029 ) 89 5,895 154 Total gain (loss) in pre-tax earnings $ 345 $ — $ (79 ) $ — UNREALIZED GAIN/LOSS. Outstanding derivative instruments related to regulated NGD operations are deferred in accordance with regulatory accounting standards. The cost of foreign currency forward and natural gas derivative contracts are recognized immediately in the cost of gas; however, costs above or below the amount embedded in the current year PGA are subject to a regulatory deferral tariff and therefore, are recorded as a regulatory asset or liability. REALIZED GAIN/LOSS. NW Natural realized net gains of $11.3 million for the three months ended March 31, 2019 , from the settlement of natural gas financial derivative contracts. Whereas, net losses of $9.0 million were realized for the three months ended March 31, 2018 . Realized gains and losses offset the higher or lower cost of gas purchased resulting in no incremental amounts to collect or refund to customers. Credit Risk Management of Financial Derivatives Instruments No collateral was posted with or by NW Natural counterparties as of March 31, 2019 or 2018 . NW Natural attempts to minimize the potential exposure to collateral calls by counterparties to manage liquidity risk. Counterparties generally allow a certain credit limit threshold before requiring NW Natural to post collateral against loss positions. Given NW Natural's counterparty credit limits and portfolio diversification, it was not subject to collateral calls in 2019 or 2018 . The collateral call exposure is set forth under credit support agreements, which generally contain credit limits. NW Natural could also be subject to collateral call exposure where it has agreed to provide adequate assurance, which is not specific as to the amount of credit limit allowed, but could potentially require additional collateral in the event of a material adverse change. Based upon current commodity financial swap and option contracts outstanding, which reflect unrealized losses of $0.5 million at March 31, 2019 , we have estimated the level of collateral demands, with and without potential adequate assurance calls, using current gas prices and various credit downgrade rating scenarios for NW Natural as follows: Credit Rating Downgrade Scenarios In thousands (Current Ratings) A+/A3 BBB+/Baa1 BBB/Baa2 BBB-/Baa3 Speculative With Adequate Assurance Calls $ — $ — $ — $ — $ 604 Without Adequate Assurance Calls — — — — 185 NW Natural's financial derivative instruments are subject to master netting arrangements; however, they are presented on a gross basis in the consolidated balance sheets. NW Natural and its counterparties have the ability to set-off obligations to each other under specified circumstances. Such circumstances may include a defaulting party, a credit change due to a merger affecting either party, or any other termination event. If netted by counterparty, NW Natural's physical and financial derivative position would result in an asset of $6.4 million and a liability of $2.0 million as of March 31, 2019 , an asset of $ 2.2 million and a liability of $ 19.9 million as of March 31, 2018 , and an asset of $3.6 million and a liability of $9.3 million as of December 31, 2018 . NW Natural is exposed to derivative credit and liquidity risk primarily through securing fixed price natural gas commodity swaps to hedge the risk of price increases for natural gas purchases made on behalf of customers. See Note 15 in the 2018 Form 10-K for additional information. Fair Value In accordance with fair value accounting, NW Natural includes non-performance risk in calculating fair value adjustments. This includes a credit risk adjustment based on the credit spreads of NW Natural counterparties when in an unrealized gain position, or on NW Natural's own credit spread when in an unrealized loss position. The inputs in our valuation models include natural gas futures, volatility, credit default swap spreads and interest rates. Additionally, the assessment of non-performance risk is generally derived from the credit default swap market and from bond market credit spreads. The impact of the credit risk adjustments for all outstanding derivatives was immaterial to the fair value calculation at March 31, 2019 . Using significant other observable or Level 2 inputs, the net fair value was an asset of $ 4.4 million , a liability of $ 17.7 million , and a liability of $5.7 million as of March 31, 2019 and 2018 , and December 31, 2018 , respectively. No Level 3 inputs were used in our derivative valuations, and there were no transfers between Level 1 or Level 2 during the three months ended March 31, 2019 and 2018 . See Note 2 in the 2018 Form 10-K.

Environmental Matters

Environmental Matters	3 Months Ended
	Mar. 31, 2019
Environmental Remediation Obligations [Abstract]
Environmental Matters	ENVIRONMENTAL MATTERS NW Natural owns, or previously owned, properties that may require environmental remediation or action. The range of loss for environmental liabilities is estimated based on current remediation technology, enacted laws and regulations, industry experience gained at similar sites, and an assessment of the probable level of involvement and financial condition of other potentially responsible parties (PRPs). When amounts are prudently expended related to site remediation of those sites described herein, NW Natural has a recovery mechanism in place to collect 96.68% of remediation costs allocable to Oregon customers, and NW Natural is allowed to defer environmental remediation costs allocated to customers in Washington annually until they are reviewed for prudence at a subsequent proceeding. These sites are subject to the remediation process prescribed by the Environmental Protection Agency (EPA) and the Oregon Department of Environmental Quality (ODEQ). The process begins with a remedial investigation (RI) to determine the nature and extent of contamination and then a risk assessment (RA) to establish whether the contamination at the site poses unacceptable risks to humans and the environment. Next, a feasibility study (FS) or an engineering evaluation/cost analysis (EE/CA) evaluates various remedial alternatives. It is at this point in the process when NW Natural is able to estimate a range of remediation costs and record a reasonable potential remediation liability, or make an adjustment to the existing liability. From this study, the regulatory agency selects a remedy and issues a Record of Decision (ROD). After a ROD is issued, NW Natural would seek to negotiate a consent decree or consent judgment for designing and implementing the remedy. NW Natural would have the ability to further refine estimates of remediation liabilities at that time. Remediation may include treatment of contaminated media such as sediment, soil and groundwater, removal and disposal of media, institutional controls such as legal restrictions on future property use, or natural recovery. Following construction of the remedy, the EPA and ODEQ also have requirements for ongoing maintenance, monitoring and other post-remediation care that may continue for many years. Where appropriate and reasonably known, NW Natural will provide for these costs in the remediation liabilities described below. Due to the numerous uncertainties surrounding the course of environmental remediation and the preliminary nature of several site investigations, in some cases, NW Natural may not be able to reasonably estimate the high end of the range of possible loss. In those cases, the nature of the possible loss has been disclosed, as has the fact that the high end of the range cannot be reasonably estimated where a range of potential loss is available. Unless there is an estimate within the range of possible losses that is more likely than other cost estimates within that range, NW Natural records the liability at the low end of this range. It is likely changes in these estimates and ranges will occur throughout the remediation process for each of these sites due to the continued evaluation and clarification concerning responsibility, the complexity of environmental laws and regulations and the determination by regulators of remediation alternatives. In addition to remediation costs, NW Natural could also be subject to Natural Resource Damages (NRD) claims. NW Natural will assess the likelihood and probability of each claim and recognize a liability if deemed appropriate. Refer to " Other Portland Harbor " below. Environmental Sites The following table summarizes information regarding liabilities related to environmental sites, which are recorded in other current liabilities and other noncurrent liabilities in NW Natural's balance sheet: Current Liabilities Non-Current Liabilities March 31, December 31, March 31, December 31, In thousands 2019 2018 2018 2019 2018 2018 Portland Harbor site: Gasco/Siltronic Sediments $ 4,595 $ 2,797 $ 5,117 $ 44,427 $ 45,015 $ 44,351 Other Portland Harbor 2,299 1,769 2,600 5,958 3,928 6,273 Gasco/Siltronic Upland site 11,951 11,408 13,983 43,800 46,769 44,830 Central Service Center site 10 25 10 — — — Front Street site 11,288 764 11,402 — 10,720 3 Oregon Steel Mills — — — 179 179 179 Total $ 30,143 $ 16,763 $ 33,112 $ 94,364 $ 106,611 $ 95,636 PORTLAND HARBOR SITE. The Portland Harbor is an EPA listed Superfund site that is approximately 10 miles long on the Willamette River and is adjacent to NW Natural's Gasco uplands site. NW Natural is one of over one hundred PRPs to the Superfund site. In January 2017, the EPA issued its Record of Decision, which selects the remedy for the clean-up of the Portland Harbor site (Portland Harbor ROD). The Portland Harbor ROD estimates the present value total cost at approximately $1.05 billion with an accuracy between -30% and +50% of actual costs. NW Natural's potential liability is a portion of the costs of the remedy for the entire Portland Harbor Superfund site. The cost of that remedy is expected to be allocated among more than 100 PRPs. In addition, NW Natural is actively pursuing clarification and flexibility under the ROD in order to better understand its obligation under the clean-up. NW Natural is also participating in a non-binding allocation process with the other PRPs in an effort to resolve its potential liability. The Portland Harbor ROD does not provide any additional clarification around allocation of costs among PRPs and, as a result of issuance of the Portland Harbor ROD, NW Natural has not modified any of the recorded liabilities at this time. NW Natural manages the liability related to the Superfund site as two distinct remediation projects: the Gasco/Siltronic Sediments and Other Portland Harbor projects. Gasco/Siltronic Sediments. In 2009, NW Natural and Siltronic Corporation entered into a separate Administrative Order on Consent with the EPA to evaluate and design specific remedies for sediments adjacent to the Gasco uplands and Siltronic uplands sites. NW Natural submitted a draft EE/CA to the EPA in May 2012 to provide the estimated cost of potential remedial alternatives for this site. At this time, the estimated costs for the various sediment remedy alternatives in the draft EE/CA for the additional studies and design work needed before the cleanup can occur, and for regulatory oversight throughout the clean-up range from $49.0 million to $350 million . NW Natural has recorded a liability of $49.0 million for the sediment clean-up, which reflects the low end of the range. At this time, NW Natural believes sediments at this site represent the largest portion of its liability related to the Portland Harbor site discussed above. Other Portland Harbor. While we believe liabilities associated with the Gasco/Siltronic sediments site represent NW Natural's largest exposure, there are other potential exposures associated with the Portland Harbor ROD, including NRD costs and harborwide clean-up costs (including downstream petroleum contamination), for which allocations among the PRPs have not yet been determined. NW Natural and other parties have signed a cooperative agreement with the Portland Harbor Natural Resource Trustee council to participate in a phased NRD assessment to estimate liabilities to support an early restoration-based settlement of NRD claims. One member of this Trustee council, the Yakama Nation, withdrew from the council in 2009, and in 2017, filed suit against NW Natural and 29 other parties seeking remedial costs and NRD assessment costs associated with the Portland Harbor site, set forth in the complaint. The complaint seeks recovery of alleged costs totaling $0.3 million in connection with the selection of a remedial action for the Portland Harbor site as well as declaratory judgment for unspecified future remedial action costs and for costs to assess the injury, loss or destruction of natural resources resulting from the release of hazardous substances at and from the Portland Harbor site. The Yakama Nation has filed two amended complaints addressing certain pleading defects and dismissing the State of Oregon. The Magistrate Judge has recommended granting NW Natural and certain other defendants' motion to stay the case. NW Natural has recorded a liability for NRD claims which is at the low end of the range of the potential liability; the high end of the range cannot be reasonably estimated at this time. The NRD liability is not included in the aforementioned range of costs provided in the Portland Harbor ROD. GASCO UPLANDS SITE. A predecessor of NW Natural, Portland Gas and Coke Company, owned a former gas manufacturing plant that was closed in 1958 (Gasco site) and is adjacent to the Portland Harbor site described above. The Gasco site has been under investigation by NW Natural for environmental contamination under the ODEQ Voluntary Clean-Up Program (VCP). It is not included in the range of remedial costs for the Portland Harbor site noted above. The Gasco site is managed in two parts, the uplands portion and the groundwater source control action. NW Natural submitted a revised Remedial Investigation Report for the uplands to ODEQ in May 2007. In March 2015, ODEQ approved the RA, enabling commencement of work on the FS in 2016. NW Natural has recognized a liability for the remediation of the uplands portion of the site which is at the low end of the range of potential liability; the high end of the range cannot be reasonably estimated at this time. In October 2016, ODEQ and NW Natural agreed to amend their VCP agreement to incorporate a portion of the Siltronic property adjacent to the Gasco site formerly owned by Portland Gas & Coke between 1939 and 1960 into the Gasco RA and FS, excluding the uplands for Siltronic. Previously, NW Natural was conducting an investigation of manufactured gas plant constituents on the entire Siltronic uplands for ODEQ. Siltronic will be working with ODEQ directly on environmental impacts to the remainder of its property. In September 2013, NW Natural completed construction of a groundwater source control system, including a water treatment station, at the Gasco site. NW Natural has estimated the cost associated with the ongoing operation of the system and has recognized a liability which is at the low end of the range of potential cost. NW Natural cannot estimate the high end of the range at this time due to the uncertainty associated with the duration of running the water treatment station, which is highly dependent on the remedy determined for both the upland portion as well as the final remedy for Gasco sediment exposure. OTHER SITES. In addition to those sites above, NW Natural has environmental exposures at three other sites: Central Service Center, Front Street and Oregon Steel Mills. NW Natural may have exposure at other sites that have not been identified at this time. Due to the uncertainty of the design of remediation, regulation, timing of the remediation and in the case of the Oregon Steel Mills site, pending litigation, liabilities for each of these sites have been recognized at their respective low end of the range of potential liability; the high end of the range could not be reasonably estimated at this time. Central Service Center site. NW Natural is currently performing an environmental investigation of the property under ODEQ's Independent Cleanup Pathway. This site is on ODEQ's list of sites with confirmed releases of hazardous substances, and cleanup is necessary. Front Street site. The Front Street site was the former location of a gas manufacturing plant NW Natural operated (the former Portland Gas Manufacturing site, or PGM). At ODEQ’s request, NW Natural conducted a sediment and source control investigation and provided findings to ODEQ. In December 2015, an FS on the former Portland Gas Manufacturing site was completed. In July 2017, ODEQ issued the PGM ROD. The ROD specifies the selected remedy, which requires a combination of dredging, capping, treatment, and natural recovery. In addition, the selected remedy also requires institutional controls and long-term inspection and maintenance. NW Natural revised the liability in the second quarter of 2017 to incorporate the estimated undiscounted cost of approximately $10.5 million for the selected remedy. Further, NW Natural has recognized an additional liability of $0.8 million for additional studies and design costs as well as regulatory oversight throughout the clean-up. NW Natural plans to complete the remedial design in early 2019 and currently expects to construct the remedy during 2019. Oregon Steel Mills site. Refer to the “Legal Proceedings,” below. Site Remediation and Recovery Mechanism (SRRM) NW Natural has an SRRM through which it tracks and has the ability to recover past deferred and future prudently incurred environmental remediation costs allocable to Oregon, subject to an earnings test, for those sites identified therein. See Note 17 in the 2018 Form 10-K for a description of the SRRM collection process. The following table presents information regarding the total regulatory asset deferred: March 31, December 31, In thousands 2019 2018 2018 Deferred costs and interest (1) $ 36,874 $ 44,686 $ 41,883 Accrued site liabilities (2) 124,133 122,962 128,369 Insurance proceeds and interest (89,305 ) (95,100 ) (88,502 ) Total regulatory asset deferral (1) $ 71,702 $ 72,548 $ 81,750 Current regulatory assets (3) 5,090 5,818 5,601 Long-term regulatory assets (3) 66,612 66,730 76,149 (1) Includes pre-review and post-review deferred costs, amounts currently in amortization, and interest, net of amounts collected from customers. (2) Excludes 3.32% of the Front Street site liability, or $0.4 million in 2019 and $0.4 million in 2018 , as the OPUC only allows recovery of 96.68% of costs for those sites allocable to Oregon, including those that historically served only Oregon customers. (3) Environmental costs relate to specific sites approved for regulatory deferral by the OPUC and WUTC. In Oregon, NW Natural earns a carrying charge on cash amounts paid, whereas amounts accrued but not yet paid do not earn a carrying charge until expended. It also accrues a carrying charge on insurance proceeds for amounts owed to customers. In Washington, a carrying charge related to deferred amounts will be determined in a future proceeding. Current environmental costs represent remediation costs management expects to collect from customers in the next 12 months. Amounts included in this estimate are still subject to a prudence and earnings test review by the OPUC and do not include the $5.0 million tariff rider. The amounts allocable to Oregon are recoverable through NGD rates, subject to an earnings test. ENVIRONMENTAL EARNINGS TEST. To the extent NW Natural earns at or below its authorized Return on Equity (ROE) as defined by the SRRM, remediation expenses and interest in excess of the $5.0 million tariff rider and $5.0 million insurance proceeds are recoverable through the SRRM. To the extent that NW Natural earns more than its authorized ROE in a year, it is required to cover environmental expenses and interest on expenses greater than the $10.0 million with those earnings that exceed its authorized ROE. At March 31, 2019 NW Natural reserved approximately $4.4 million related to this mechanism. Under the 2015 Order, the OPUC stated they would revisit the deferral and amortization of future remediation expenses, as well as the treatment of remaining insurance proceeds three years from the original Order, or earlier if NW Natural gains greater certainty about future remediation costs, to consider whether adjustments to the mechanism may be appropriate. NW Natural filed an update with the OPUC in March 2018 and recommended no changes. WASHINGTON DEFERRAL. Cost recovery and carrying charges on amounts deferred for costs associated with services provided to Washington customers will be determined in a future proceeding. Legal Proceedings Other than the matters discussed above, NW Holdings is not currently party to any direct claims or litigation, though in the future it may be subject to claims and litigation arising in the ordinary course of business. NW Natural is subject to claims and litigation arising in the ordinary course of business. Although the final outcome of any of these legal proceedings cannot be predicted with certainty, including the matter described below, NW Natural and NW Holdings do not expect that the ultimate disposition of any of these matters will have a material effect on financial condition, results of operations or cash flows. See also Part II, Item 1, “ Legal Proceedings" . OREGON STEEL MILLS SITE. See Note 17 in the 2018 Form 10-K. For additional information regarding other commitments and contingencies, see Note 16 in the 2018 Form 10-K.

Discontinued Operations

Discontinued Operations	3 Months Ended
	Mar. 31, 2019
Discontinued Operations and Disposal Groups [Abstract]
Discontinued Operations	DISCONTINUED OPERATIONS NW Holdings On June 20, 2018, NWN Gas Storage, then a wholly owned subsidiary of NW Natural, entered into a Purchase and Sale Agreement (the Agreement) that provides for the sale by NWN Gas Storage of all of the membership interests in Gill Ranch. Gill Ranch owns a 75% interest in the natural gas storage facility located near Fresno, California known as the Gill Ranch Gas Storage Facility. Pacific Gas and Electric Company (PG&E) owns the remaining 25% interest in the Gill Ranch Gas Storage Facility. The CPUC regulates Gill Ranch under a market-based rate model which allows for the price of storage services to be set by the marketplace. The CPUC also regulates the issuance of securities, system of accounts, and regulates intrastate storage services. The Agreement provides for an initial cash purchase price of $25.0 million (subject to a working capital adjustment), plus potential additional payments to NWN Gas Storage of up to $26.5 million in the aggregate if Gill Ranch achieves certain economic performance levels for the first three full gas storage years (April 1 of one year through March 31 of the following year) occurring after the closing and the remaining portion of the gas storage year during which the closing occurs. We expect the transaction to close in 2019. The closing of the transaction is subject to approval by the CPUC and other customary closing conditions. In July 2018, Gill Ranch filed an application with the CPUC for approval of this transaction. On February 14, 2019, the active parties to the CPUC proceeding filed a settlement agreement with the CPUC. The CPUC is expected to rule on the settlement agreement within 90 days of its filing, but may grant further time for public comment. We expect an order on this matter by the end of June 2019. As a result of the strategic shift away from the California gas storage market and the significance of Gill Ranch's financial results in 2017, we concluded that the pending sale of Gill Ranch qualified it as assets and liabilities held for sale and discontinued operations. As such, the assets and liabilities associated with Gill Ranch have been classified as discontinued operations assets and discontinued operations liabilities, respectively, and, the results of Gill Ranch are presented, net of tax, as discontinued operations separately from the results of continuing operations for all periods presented. The expenses included in the results of discontinued operations are the direct operating expenses incurred by Gill Ranch that may be reasonably segregated from the costs of NW Holdings' continuing operations. The following table presents the carrying amounts of the major components of Gill Ranch that are classified as discontinued operations assets and liabilities on the consolidated balance sheets: NW Holdings Discontinued Operations March 31, December 31, In thousands 2019 2018 2018 Assets: Accounts receivable $ 1,277 $ 193 $ 390 Inventories 627 736 685 Other current assets 337 583 333 Property, plant, and equipment 12,033 10,812 11,621 Less: Accumulated depreciation 7 4 7 Operating lease right of use asset 118 — — Other non-current assets 247 51 247 Discontinued operations - current assets (1) 14,632 1,512 13,269 Discontinued operations - non-current assets (1) — 10,859 — Total discontinued operations assets $ 14,632 $ 12,371 $ 13,269 Liabilities: Accounts payable $ 1,102 $ 462 $ 873 Taxes accrued 59 334 — Other current liabilities 300 413 307 Operating lease liabilities 111 — — Other non-current liabilities 11,710 11,979 11,779 Discontinued operations - current liabilities (1) 13,282 1,209 12,959 Discontinued operations - non-current liabilities (1) — 11,979 — Total discontinued operations liabilities $ 13,282 $ 13,188 $ 12,959 (1) The total assets and liabilities of Gill Ranch are classified as current as of March 31, 2019 and December 31, 2018 because it is probable that the sale will be completed within one year. The following table presents the operating results of Gill Ranch, which was reported within the gas storage segment historically, and is presented net of tax on the consolidated statements of comprehensive income: NW Holdings Discontinued Operations Three Months Ended March 31, In thousands, except per share data 2019 2018 Revenues $ 1,721 $ 1,077 Expenses: Operations and maintenance 1,613 1,036 General taxes 59 334 Depreciation and amortization 106 110 Other expenses and interest 237 241 Total expenses 2,015 1,721 Loss from discontinued operations before income taxes (294 ) (644 ) Income tax benefit (77 ) (170 ) Loss from discontinued operations, net of tax $ (217 ) $ (474 ) Loss from discontinued operations per share of common stock: Basic $ (0.01 ) $ (0.02 ) Diluted (0.01 ) (0.02 ) NW Natural As a result of the holding company reorganization in October 2018, NWN Energy, NWN Gas Storage, Gill Ranch, NNG Financial, NWN Water, and NW Holdings, which were direct and indirect subsidiaries of NW Natural prior to the reorganization, are no longer subsidiaries of NW Natural. As a result, NW Natural's financial statements reflect amounts related to these entities as discontinued operations for all periods presented. The expenses included in the results of discontinued operations are the direct operating expenses incurred by the entities that may be reasonably segregated from the costs of NW Natural's continuing operations. The following table presents the carrying amounts of the major components of NWN Energy, NWN Gas Storage, Gill Ranch, NNG Financial, NWN Water, and NW Holdings that are classified as discontinued operations assets and liabilities on NW Natural's consolidated balance sheets: NW Natural Discontinued Operations In thousands March 31, 2018 Assets: Cash $ 311 Accounts receivable 193 Receivables from affiliates 3,852 Inventories 736 Other current assets 639 Property, plant, and equipment 11,186 Less: Accumulated depreciation 203 Other investments 13,691 Other non-current assets 64 Discontinued operations - current assets 5,731 Discontinued operations - non-current assets 24,738 Total discontinued operations assets $ 30,469 Liabilities: Accounts payable $ 731 Taxes accrued 368 Payables to affiliates 660 Other current liabilities 401 Deferred tax liabilities (16,397 ) Other non-current liabilities 12,067 Discontinued operations - current liabilities 2,160 Discontinued operations - non-current liabilities (4,330 ) Total discontinued operations liabilities $ (2,170 ) The following table presents the operating results prior to the holding company reorganization effective October 1, 2018 of NWN Energy, NWN Gas Storage, Gill Ranch, NNG Financial, NWN Water, and NW Holdings, which were historically reported within the gas storage segment and other, and is presented net of tax on NW Natural's consolidated statements of comprehensive income: NW Natural Discontinued Operations Three Months Ended March 31, In thousands, except per share data 2018 Revenues $ 1,133 Expenses: Operations and maintenance 1,059 General taxes 347 Depreciation and amortization 117 Other expenses and interest 260 Total expenses 1,783 Loss from discontinued operations before income taxes (650 ) Income tax benefit (173 ) Loss from discontinued operations, net of tax $ (477 )

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Industry Regulation	Industry Regulation In applying regulatory accounting principles, NW Holdings and NW Natural capitalize or defer certain costs and revenues as regulatory assets and liabilities pursuant to orders of the Oregon Public Utilities Commission (OPUC), Washington Utilities and Transportation Commission (WUTC) or Idaho Public Utilities Commission (IPUC), which provide for the recovery of revenues or expenses from, or refunds to, utility customers in future periods, including a return or a carrying charge in certain cases.
New Accounting Standards	New Accounting Standards We consider the applicability and impact of all accounting standards updates (ASUs) issued by the Financial Accounting Standards Board (FASB). ASUs not listed below were assessed and determined to be either not applicable or are expected to have minimal impact on NW Natural's consolidated financial position or results of operations. Recently Adopted Accounting Pronouncements ACCUMULATED OTHER COMPREHENSIVE INCOME. On February 14, 2018, the FASB issued ASU 2018-02, "Income Statement—Reporting Comprehensive Income: Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income." This update was issued in response to concerns from certain stakeholders regarding the current requirements under U.S. GAAP that deferred tax assets and liabilities are adjusted for a change in tax laws or rates, and the effect is to be included in income from continuing operations in the period of the enactment date. This requirement is also applicable to items in accumulated other comprehensive income where the related tax effects were originally recognized in other comprehensive income. The adjustment of deferred taxes due to the new corporate income tax rate enacted through the Tax Cuts and Jobs Act (TCJA) on December 22, 2017 recognized in income from continuing operations causes the tax effects of items within accumulated other comprehensive income (referred to as stranded tax effects) to not reflect the appropriate tax rate. The amendments in this update allow but do not require a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the TCJA and require certain disclosures about stranded tax effects. NW Natural adopted and applied the standard in the first quarter of 2019. NW Natural elected to reclassify the stranded tax effects of the TJCA of $1.4 million from accumulated other comprehensive loss to retained earnings in the period of adoption. Going forward, our policy is that, in the event that regulation changes result in stranded tax effects, such amounts will be reclassified from accumulated other comprehensive income (loss) to retained earnings in the final period that the related deferred tax balance remeasurement is expected to impact income from continuing operations. DERIVATIVES AND HEDGING. On August 28, 2017, the FASB issued ASU 2017-12, "Derivatives and Hedging: Targeted Improvements to Accounting for Hedging Activities." The purpose of the amendment is to more closely align hedge accounting with companies’ risk management strategies. The ASU amends the accounting for risk component hedging, the hedged item in fair value hedges of interest rate risk, and amounts excluded from the assessment of hedge effectiveness. The guidance also amends the recognition and presentation of the effect of hedging instruments and includes other simplifications of hedge accounting. The amendments in this update were effective beginning January 1, 2019 and were applied prospectively to hedging instruments. The adoption did not have an impact on the financial statements or disclosures of NW Holdings or NW Natural. GOODWILL. On January 26, 2017, the FASB issued ASU 2017-04, "Simplifying the Test for Goodwill Impairment." The ASU removes Step 2 from the goodwill impairment test and under the amended guidance an entity should perform its annual goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount and recognize an impairment charge for the amount in which the carrying amounts exceed the fair value of the reporting unit. The amendments in this standard are effective for us beginning January 1, 2020 and early adoption is permitted for interim or annual goodwill impairment tests performed after January 1, 2017. NW Natural early adopted ASU 2017-04 in the quarter ended September 30, 2018. The adoption of this ASU did not materially affect the financial statements and disclosures of NW Holdings or NW Natural. LEASES. On February 25, 2016, the FASB issued ASU 2016-02, "Leases," which revises the existing lease accounting guidance. Pursuant to the new standard (“ASC 842”), lessees are required to recognize all leases, including operating leases that are greater than 12 months at lease commencement, on the balance sheet and record corresponding right of use assets and lease liabilities. Lessor accounting will remain substantially the same under the new standard. Quantitative and qualitative disclosures are also required for users of the financial statements to have a clear understanding of the nature of our leasing activities. We elected the alternative prospective transition approach for adoption beginning January 1, 2019. All comparative periods prior to January 1, 2019 will retain the financial reporting and disclosure requirements of ASC 840 “Leases” (“ASC 840”). There was no cumulative effect adjustment to the opening balance of retained earnings recorded as of January 1, 2019 for adoption as there were no initial direct costs or other capitalized costs related to the legacy leases that needed to be derecognized upon adoption of ASC 842. We elected the land easement optional practical expedient to not evaluate existing or expired land easements that were not previously accounted for as leases under the ASC 840 lease guidance. For the existing lease portfolio, we did not elect the optional practical expedient package to retain the legacy lease accounting conclusions upon adoption; we re-assessed our existing contracts under the new leasing standard including whether the contract meets the definition of a lease and lease classification. As a result, we determined that most of our underground gas storage contracts no longer meet the definition of a lease under the new lease standard. Our lease portfolio under the new standard consists primarily of our current leased headquarters, which expires in 2020. In October 2017, NW Natural entered into a 20-year operating lease agreement commencing in 2020 for a new headquarters location in Portland, Oregon. The lease was analyzed under ASC 840 in consideration of build-to-suit lease accounting guidance with the conclusion that NW Natural was the accounting owner of the asset during construction. Under the new lease standard, ASC 842, NW Natural is no longer considered the accounting owner of the asset during construction. As such, in January 2019 we derecognized the build-to-suit asset and liability balances of $26.0 million as of December 31, 2018 that were previously recorded within property, plant and equipment and other non-current liabilities in the consolidated balance sheet. Upon adoption on January 1, 2019, NW Holdings recorded an operating lease right of use asset and an associated operating lease liability of approximately $7.3 million , of which $7.0 million was recorded at NW Natural. Lease liabilities are measured using NW Natural's incremental borrowing rate based on information available at the lease commencement date in determining the present value of lease payments. See Note 6 . CLOUD COMPUTING. On August 29, 2018, the FASB issued ASU 2018-15, "Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract." The purpose of the amendment is to align the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. The amendments in this update are effective for us beginning January 1, 2020. Early adoption is permitted, and NW Holdings and NW Natural early adopted ASU 2018-15 in the quarter ended March 31, 2019 utilizing the prospective application methodology. The adoption of this ASU did not materially affect the financial statements and disclosures of NW Holdings or NW Natural. Recently Issued Accounting Pronouncements RETIREMENT BENEFITS. On August 28, 2018, the FASB issued ASU 2018-14, "Changes to the Disclosure Requirements for Defined Benefit Plans." The purpose of the amendment is to modify the disclosure requirements for defined benefit pension and other postretirement plans. The amendments in this update are effective for us beginning January 1, 2020. Early adoption is permitted. The amended presentation and disclosure guidance should be applied retrospectively. We are currently assessing the effect of this standard on disclosures. FAIR VALUE MEASUREMENT. On August 28, 2018, the FASB issued ASU 2018-13, "Changes to the Disclosure Requirements for Fair Value Measurement." The purpose of the amendment is to modify the disclosure requirements for fair value measurements. The amendments in this update are effective for us beginning January 1, 2020. Early adoption is permitted. The amendments on changes in unrealized gains and losses, the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements and the narrative description of measurement uncertainty should be applied prospectively. All other amendments should be applied retrospectively. We are currently assessing the effect of this standard on disclosures. CREDIT LOSSES. On June 16, 2016, the FASB issued ASU 2016-13, "Measurement of Credit Losses on Financial Instruments," which applies to financial assets subject to credit losses and measured at amortized cost. The new standard will require financial assets measured at amortized cost to be presented at the net amount expected to be collected and the allowance for credit losses is to be recorded as a valuation account that is deducted from the amortized cost basis. The amendments in this update are effective beginning January 1, 2020. Early adoption is permitted for fiscal years beginning after December 15, 2018. We are currently assessing the effect of this standard on our financial statements and disclosures.

Significant Accounting Polici_3

Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Schedule of Regulatory Assets	Amounts deferred as regulatory assets and liabilities were as follows: Regulatory Assets March 31, December 31, In thousands 2019 2018 2018 Current: Unrealized loss on derivatives (1) $ 2,845 $ 17,569 $ 12,381 Gas costs 17,927 591 2,873 Environmental costs (2) 5,090 5,818 5,601 Decoupling (3) 3,937 9,578 9,140 Pension balancing (4) 4,955 — — Income taxes 2,209 2,218 2,218 Other (5) 9,354 10,126 9,717 Total current $ 46,317 $ 45,900 $ 41,930 Non-current: Unrealized loss on derivatives (1) $ 1,161 $ 2,355 $ 3,025 Pension balancing (4) 50,408 63,940 74,173 Income taxes 17,758 19,267 19,185 Pension and other postretirement benefit liabilities 171,565 175,505 174,993 Environmental costs (2) 66,612 66,730 76,149 Gas costs 8,919 49 9,978 Decoupling (3) 250 2,663 2,545 Other (5) 10,521 12,528 11,738 Total non-current $ 327,194 $ 343,037 $ 371,786
Schedule of Regulatory Liabilities	Regulatory Liabilities March 31, December 31, In thousands 2019 2018 2018 Current: Gas costs $ 11,126 $ 17,798 $ 17,182 Unrealized gain on derivatives (1) 7,284 1,120 8,740 Decoupling (3) 2,055 2,501 2,264 Income taxes 7,763 — — Other (5) 18,542 13,527 19,250 Total current $ 46,770 $ 34,946 $ 47,436 Non-current: Gas costs $ 1,421 $ 5,639 $ 552 Unrealized gain on derivatives (1) 541 1,148 725 Decoupling (3) 614 1,253 — Income taxes (6) 202,692 219,795 225,408 Accrued asset removal costs (7) 384,702 365,363 380,464 Other (5) 10,728 7,244 4,411 Total non-current $ 600,698 $ 600,442 $ 611,560 (1) Unrealized gains or losses on derivatives are non-cash items and therefore do not earn a rate of return or a carrying charge. These amounts are recoverable through NGD rates as part of the annual Purchased Gas Adjustment (PGA) mechanism when realized at settlement. (2) Refer to footnote (3) of the Deferred Regulatory Asset table in Note 16 for a description of environmental costs. (3) This deferral represents the margin adjustment resulting from differences between actual and expected volumes. (4) Refer to Note 9 for information regarding the deferral of pension expenses. (5) Balances consist of deferrals and amortizations under approved regulatory mechanisms and typically earn a rate of return or carrying charge. (6) This balance represents estimated amounts associated with the Tax Cuts and Jobs Act. See Note 10 . (7) Estimated costs of removal on certain regulated properties are collected through rates.

Earnings Per Share (Tables)

Earnings Per Share (Tables)	3 Months Ended
	Mar. 31, 2019
Earnings Per Share [Abstract]
EPS Calculation	NW Holdings' diluted earnings or loss per share are calculated as follows: Three Months Ended March 31, In thousands, except per share data 2019 2018 Net Income from continuing operations $ 43,418 $ 42,011 Loss from discontinued operations, net of tax (217 ) (474 ) Net income $ 43,201 $ 41,537 Average common shares outstanding - basic 28,906 28,753 Additional shares for stock-based compensation plans (See Note 7) 64 50 Average common shares outstanding - diluted 28,970 28,803 Earnings from continuing operations per share of common stock: Basic $ 1.50 $ 1.46 Diluted $ 1.50 $ 1.46 Loss from discontinued operations per share of common stock: Basic $ (0.01 ) $ (0.02 ) Diluted $ (0.01 ) $ (0.02 ) Earnings per share of common stock: Basic $ 1.49 $ 1.44 Diluted $ 1.49 $ 1.44 Additional information: Antidilutive shares 5 16

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2019
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, by Segment	The following table presents summary financial information concerning the reportable segments of continuing operations. See Note 17 for information regarding discontinued operations for NW Holdings and NW Natural. Three Months Ended March 31, In thousands NGD Other (NW Natural) NW Natural Other (NW Holdings) NW Holdings 2019 Operating revenues $ 279,041 $ 5,805 $ 284,846 $ 502 $ 285,348 Depreciation and amortization 21,249 255 21,504 68 21,572 Income (loss) from operations 72,898 3,746 76,644 (599 ) 76,045 Net income (loss) from continuing operations 41,206 2,689 43,895 (477 ) 43,418 Capital expenditures 48,606 52 48,658 106 48,764 Total assets at March 31, 2019 (1) 3,091,062 49,566 3,140,628 35,857 3,176,485 2018 Operating revenues $ 257,933 $ 5,702 $ 263,635 $ — $ 263,635 Depreciation and amortization 20,543 325 20,868 7 20,875 Income from operations 64,756 2,982 67,738 13 67,751 Net income (loss) from continuing operations 39,883 2,131 42,014 (3 ) 42,011 Capital expenditures 56,894 435 57,329 — 57,329 Total assets at March 31, 2018 (1) 2,952,294 50,850 3,003,144 13,824 3,016,968 Total assets at December 31, 2018 (1) 3,141,969 50,767 3,192,736 36,657 3,229,393 (1) Total assets for NW Holdings exclude assets related to discontinued operations of $14.6 million , $12.4 million , and $13.3 million as of March 31, 2019 , March 31, 2018 , and December 31, 2018 , respectively. Total assets for NW Natural exclude assets related to discontinued operations of $30.5 million as of March 31, 2018 .
NGD Margin	The following table presents additional segment information concerning NGD margin: Three Months Ended March 31, In thousands 2019 2018 NGD margin calculation: NGD operating revenues $ 279,041 $ 257,933 Less: NGD cost of gas 105,513 108,164 Environmental remediation expense 8,947 4,624 Revenue taxes 11,926 12,429 NGD margin $ 152,655 $ 132,716

Leases (Tables)

Leases (Tables)	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Leases [Abstract]
Lease Revenue	The components of lease revenue at NW Natural were as follows: In thousands Three months ended March 31, 2019 Lease revenue Operating leases $ 48 Sales-type leases 60 Total lease revenue $ 108
Lessor, Operating Lease, Payments to be Received, Maturity	Total future minimum lease payments to be received under non-cancelable leases at NW Natural at March 31, 2019 are as follows: In thousands Operating Sales-Type Total 2019 (excluding the three months ended March 31, 2019) $ 94 $ 286 $ 380 2020 61 212 273 2021 49 198 247 2022 45 186 231 2023 45 173 218 Thereafter 138 478 616 Total lease revenue $ 432 $ 1,533 $ 1,965 Less: imputed interest 459 Total lease receivable $ 1,074
Lease Expense	The components of lease expense, a portion of which is capitalized, were as follows: Three months ended March 31, 2019 In thousands NW Natural Other NW Holdings Operating lease expense $ 1,142 $ 46 $ 1,188 Short-term lease expense 160 — 160
Operating Lease, Lease Asset and Liabilities	Supplemental balance sheet information related to operating leases as of March 31, 2019 is as follows: In thousands NW Natural Other NW Holdings Operating lease right of use asset $ 5,903 $ 260 $ 6,163 Operating lease liabilities - current liabilities $ 4,477 $ 179 $ 4,656 Operating lease liabilities - non-current liabilities 1,413 82 1,495 Total operating lease liabilities $ 5,890 $ 261 $ 6,151
Lessee, Operating Lease, Liability, Maturity	Maturities of operating lease liabilities at March 31, 2019 were as follows: In thousands NW Natural Other NW Holdings 2019 (excluding the three months ended March 31, 2019) $ 3,462 $ 139 $ 3,601 2020 1,980 102 2,082 2021 101 28 129 2022 93 — 93 2023 71 — 71 Thereafter 497 — 497 Total lease payments 6,204 269 6,473 Less: imputed interest 314 8 322 Total lease obligations 5,890 261 6,151 Less: current obligations 4,477 179 4,656 Long-term lease obligations $ 1,413 $ 82 $ 1,495	The following table reflects NW Natural's future minimum lease payments due under non-cancelable operating leases for continuing operations at December 31, 2018 . These commitments relate principally to the lease of the office headquarters and underground gas storage facilities. In thousands Minimum lease payments 2019 $ 5,368 2020 4,812 2021 7,077 2022 7,223 2023 7,304 Thereafter 149,881 Total $ 181,665
Lessee, Leases, Supplemental Cash Flow Information	Supplemental cash flow information related to leases was as follows: Three months ended March 31, 2019 In thousands NW Natural Other NW Holdings Cash paid for amounts included in the measurement of lease liabilities Operating cash flows from operating leases $ 1,091 $ 43 $ 1,134 Right of use assets obtained in exchange for lease obligations Operating leases $ 6,987 $ 304 $ 7,291

Revenue (Tables)

Revenue (Tables)	3 Months Ended
	Mar. 31, 2019
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	The following table presents disaggregated revenue from continuing operations: Three Months Ended March 31, In thousands NGD Other (NW Natural) NW Natural Other (NW Holdings) NW Holdings 2019 Natural gas sales $ 296,186 $ — $ 296,186 $ — $ 296,186 Gas storage revenue, net — 2,783 2,783 — 2,783 Asset management revenue, net — 1,506 1,506 — 1,506 Appliance retail center revenue — 1,516 1,516 — 1,516 Other revenue — — — 502 502 Revenue from contracts with customers 296,186 5,805 301,991 502 302,493 Alternative revenue (17,253 ) — (17,253 ) — (17,253 ) Leasing revenue 108 — 108 — 108 Total operating revenues $ 279,041 $ 5,805 $ 284,846 $ 502 $ 285,348 2018 Natural gas sales $ 258,229 $ — $ 258,229 $ — $ 258,229 Gas storage revenue, net — 2,577 2,577 — 2,577 Asset management revenue, net — 1,579 1,579 — 1,579 Appliance retail center revenue — 1,546 1,546 — 1,546 Other revenue — — — — — Revenue from contracts with customers 258,229 5,702 263,931 — 263,931 Alternative revenue (372 ) — (372 ) — (372 ) Leasing revenue 76 — 76 — 76 Total operating revenues $ 257,933 $ 5,702 $ 263,635 $ — $ 263,635

Debt (Tables)

Debt (Tables)	3 Months Ended
	Mar. 31, 2019
Debt Disclosure [Abstract]
Schedule of Carrying Values and Estimated Fair Values of Debt Instruments	The following table provides an estimate of the fair value of NW Natural's long-term debt, including current maturities of long-term debt, using market prices in effect on the valuation date: March 31, December 31, In thousands 2019 2018 2018 Gross long-term debt $ 739,700 $ 764,700 $ 739,700 Unamortized debt issuance costs (5,246 ) (6,418 ) (5,577 ) Carrying amount $ 734,454 $ 758,282 $ 734,123 Estimated fair value (1) $ 775,590 $ 807,288 $ 760,222 (1) Estimated fair value does not include unamortized debt issuance costs.

Pension and Other Postretirem_2

Pension and Other Postretirement Benefit Costs (Tables)	3 Months Ended
	Mar. 31, 2019
Pension and Other Postretirement Benefits Cost (Reversal of Cost) [Abstract]
Schedule of Net Benefit Costs	The following table provides the components of net periodic benefit cost for the pension and other postretirement benefit plans: Three Months Ended March 31, Pension Benefits Other Postretirement Benefits In thousands 2019 2018 2019 2018 Service cost $ 1,517 $ 1,807 $ 68 $ 80 Interest cost 4,662 4,183 281 241 Expected return on plan assets (5,207 ) (5,151 ) — — Amortization of prior service costs 2 11 (117 ) (117 ) Amortization of net actuarial loss 3,603 4,523 97 110 Net periodic benefit cost 4,577 5,373 329 314 Amount allocated to construction (586 ) (682 ) (24 ) (27 ) Amount deferred to regulatory balancing account — (2,756 ) — — Net periodic benefit cost charged to expense 3,991 1,935 305 287 Regulatory pension disallowance 10,500 — — — Amortization of regulatory balancing account 12,511 — — — Net amount charged to expense $ 27,002 $ 1,935 $ 305 $ 287
Schedule of Amounts Recognized in Other Comprehensive Income (Loss)	The following table presents amounts recognized in accumulated other comprehensive loss (AOCL) and the changes in AOCL related to non-qualified employee benefit plans: Three Months Ended March 31, In thousands 2019 2018 Beginning balance $ (7,188 ) $ (8,438 ) Amounts reclassified from AOCL: Amortization of actuarial losses 156 209 Reclassification of stranded tax effects (1) (1,366 ) — Total reclassifications before tax (1,210 ) 209 Tax (benefit) expense (41 ) (55 ) Total reclassifications for the period (1,251 ) 154 Ending balance $ (8,439 ) $ (8,284 ) (1) Reclassification of $1.4 million of income tax effects resulting from the TCJA from accumulated other comprehensive loss to retained earnings was made pursuant to the adoption of ASU 2018-02. See Note 2 .

Income Tax (Tables)

Income Tax (Tables)	3 Months Ended
	Mar. 31, 2019
Income Tax Disclosure [Abstract]
Schedule of Effective Income Tax Rate Reconciliation	The effective income tax rate varied from the combined federal and state statutory tax rates due to the following: Three Months Ended March 31, NW Holdings NW Natural Dollars in thousands 2019 2018 2019 2018 Income taxes at statutory rates (federal and state) $ 14,313 $ 15,368 $ 14,485 $ 15,372 Increase (decrease): Differences required to be flowed-through by regulatory commissions (5,260 ) 849 (5,260 ) 849 Other, net (378 ) (585 ) (377 ) (586 ) Total provision for income taxes on continuing operations $ 8,675 $ 15,632 $ 8,848 $ 15,635 Effective tax rate for continuing operations 16.7 % 27.1 % 16.8 % 27.1 %

Property, Plant and Equipment_2

Property, Plant and Equipment (Tables)	3 Months Ended
	Mar. 31, 2019
Property, Plant and Equipment [Abstract]
Public Utility Property, Plant, and Equipment [Table Text Block]	The following table sets forth the major classifications of property, plant, and equipment and accumulated depreciation of continuing operations: March 31, December 31, In thousands 2019 2018 2018 NW Natural: NGD plant in service $ 3,159,754 $ 3,003,962 $ 3,134,122 NGD work in progress 204,938 177,133 204,978 Less: Accumulated depreciation 985,961 954,858 974,252 NGD plant, net 2,378,731 2,226,237 2,364,848 Other plant in service 65,283 65,353 66,009 Other construction work in progress 5,329 4,252 5,330 Less: Accumulated depreciation 18,851 17,715 18,603 Other plant, net (1) 51,761 51,890 52,736 Total property, plant, and equipment $ 2,430,492 $ 2,278,127 $ 2,417,584 Other (NW Holdings): Other plant in service $ 4,156 $ 375 $ 4,051 Less: Accumulated depreciation 305 200 263 Other plant, net (1) $ 3,851 $ 175 $ 3,788 NW Holdings: Total property, plant, and equipment $ 2,434,343 $ 2,278,302 $ 2,421,372 NW Natural and NW Holdings: Capital expenditures in accrued liabilities $ 25,035 $ 21,855 $ 23,676 (1) NW Natural p reviously reported other balances were restated due to certain assets and liabilities now being classified as discontinued operations assets and liabilities in its balance sheets. See Note 17 for further discussion.

Gas Reserves (Tables)

Gas Reserves (Tables)	3 Months Ended
	Mar. 31, 2019
Gas Reserves [Abstract]
Gas Reserves	The following table outlines NW Natural's net gas reserves investment: March 31, December 31, In thousands 2019 2018 2018 Gas reserves, current $ 16,157 $ 15,124 $ 16,647 Gas reserves, non-current 171,150 172,412 170,660 Less: Accumulated amortization 109,243 91,852 104,463 Total gas reserves (1) 78,064 95,684 82,844 Less: Deferred taxes on gas reserves 19,638 22,115 20,071 Net investment in gas reserves $ 58,426 $ 73,569 $ 62,773 (1) The net investment in additional wells included in total gas reserves was $ 4.5 million , $ 5.6 million and $ 4.8 million at March 31, 2019 and 2018 and December 31, 2018 , respectively.

Derivative Instruments (Tables)

Derivative Instruments (Tables)	3 Months Ended
	Mar. 31, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Notional Amounts of Outstanding Derivative Positions	The following table presents the absolute notional amounts related to open positions on NW Natural derivative instruments: March 31, December 31, In thousands 2019 2018 2018 Natural gas (in therms): Financial 255,550 326,080 408,850 Physical 422,825 420,200 472,275 Foreign exchange $ 7,241 $ 7,611 $ 6,936
Income Statement Presentation of Derivative Instruments	The following table reflects the income statement presentation for the unrealized gains and losses from NW Natural's derivative instruments, which also represents all derivative instruments at NW Holdings: Three Months Ended March 31, 2019 2018 In thousands Natural gas commodity Foreign exchange Natural gas commodity Foreign exchange Benefit (expense) to cost of gas $ 7,007 $ (89 ) $ (5,747 ) $ (154 ) Operating revenues (expense) 2,367 — (227 ) — Amounts deferred to regulatory accounts on balance sheet (9,029 ) 89 5,895 154 Total gain (loss) in pre-tax earnings $ 345 $ — $ (79 ) $ —
Table of Estimated Collateral Calls Table	Based upon current commodity financial swap and option contracts outstanding, which reflect unrealized losses of $0.5 million at March 31, 2019 , we have estimated the level of collateral demands, with and without potential adequate assurance calls, using current gas prices and various credit downgrade rating scenarios for NW Natural as follows: Credit Rating Downgrade Scenarios In thousands (Current Ratings) A+/A3 BBB+/Baa1 BBB/Baa2 BBB-/Baa3 Speculative With Adequate Assurance Calls $ — $ — $ — $ — $ 604 Without Adequate Assurance Calls — — — — 185

Environmental Matters (Tables)

Environmental Matters (Tables)	3 Months Ended
	Mar. 31, 2019
Environmental Remediation Obligations [Abstract]
Schedule of Environmental Loss Contingencies by Site	The following table summarizes information regarding liabilities related to environmental sites, which are recorded in other current liabilities and other noncurrent liabilities in NW Natural's balance sheet: Current Liabilities Non-Current Liabilities March 31, December 31, March 31, December 31, In thousands 2019 2018 2018 2019 2018 2018 Portland Harbor site: Gasco/Siltronic Sediments $ 4,595 $ 2,797 $ 5,117 $ 44,427 $ 45,015 $ 44,351 Other Portland Harbor 2,299 1,769 2,600 5,958 3,928 6,273 Gasco/Siltronic Upland site 11,951 11,408 13,983 43,800 46,769 44,830 Central Service Center site 10 25 10 — — — Front Street site 11,288 764 11,402 — 10,720 3 Oregon Steel Mills — — — 179 179 179 Total $ 30,143 $ 16,763 $ 33,112 $ 94,364 $ 106,611 $ 95,636
Environmental Regulatory Table	The following table presents information regarding the total regulatory asset deferred: March 31, December 31, In thousands 2019 2018 2018 Deferred costs and interest (1) $ 36,874 $ 44,686 $ 41,883 Accrued site liabilities (2) 124,133 122,962 128,369 Insurance proceeds and interest (89,305 ) (95,100 ) (88,502 ) Total regulatory asset deferral (1) $ 71,702 $ 72,548 $ 81,750 Current regulatory assets (3) 5,090 5,818 5,601 Long-term regulatory assets (3) 66,612 66,730 76,149 (1) Includes pre-review and post-review deferred costs, amounts currently in amortization, and interest, net of amounts collected from customers. (2) Excludes 3.32% of the Front Street site liability, or $0.4 million in 2019 and $0.4 million in 2018 , as the OPUC only allows recovery of 96.68% of costs for those sites allocable to Oregon, including those that historically served only Oregon customers. (3) Environmental costs relate to specific sites approved for regulatory deferral by the OPUC and WUTC. In Oregon, NW Natural earns a carrying charge on cash amounts paid, whereas amounts accrued but not yet paid do not earn a carrying charge until expended. It also accrues a carrying charge on insurance proceeds for amounts owed to customers. In Washington, a carrying charge related to deferred amounts will be determined in a future proceeding. Current environmental costs represent remediation costs management expects to collect from customers in the next 12 months. Amounts included in this estimate are still subject to a prudence and earnings test review by the OPUC and do not include the $5.0 million tariff rider. The amounts allocable to Oregon are recoverable through NGD rates, subject to an earnings test.

Discontinued Operations (Tables

Discontinued Operations (Tables)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Discontinued Operations	DISCONTINUED OPERATIONS NW Holdings On June 20, 2018, NWN Gas Storage, then a wholly owned subsidiary of NW Natural, entered into a Purchase and Sale Agreement (the Agreement) that provides for the sale by NWN Gas Storage of all of the membership interests in Gill Ranch. Gill Ranch owns a 75% interest in the natural gas storage facility located near Fresno, California known as the Gill Ranch Gas Storage Facility. Pacific Gas and Electric Company (PG&E) owns the remaining 25% interest in the Gill Ranch Gas Storage Facility. The CPUC regulates Gill Ranch under a market-based rate model which allows for the price of storage services to be set by the marketplace. The CPUC also regulates the issuance of securities, system of accounts, and regulates intrastate storage services. The Agreement provides for an initial cash purchase price of $25.0 million (subject to a working capital adjustment), plus potential additional payments to NWN Gas Storage of up to $26.5 million in the aggregate if Gill Ranch achieves certain economic performance levels for the first three full gas storage years (April 1 of one year through March 31 of the following year) occurring after the closing and the remaining portion of the gas storage year during which the closing occurs. We expect the transaction to close in 2019. The closing of the transaction is subject to approval by the CPUC and other customary closing conditions. In July 2018, Gill Ranch filed an application with the CPUC for approval of this transaction. On February 14, 2019, the active parties to the CPUC proceeding filed a settlement agreement with the CPUC. The CPUC is expected to rule on the settlement agreement within 90 days of its filing, but may grant further time for public comment. We expect an order on this matter by the end of June 2019. As a result of the strategic shift away from the California gas storage market and the significance of Gill Ranch's financial results in 2017, we concluded that the pending sale of Gill Ranch qualified it as assets and liabilities held for sale and discontinued operations. As such, the assets and liabilities associated with Gill Ranch have been classified as discontinued operations assets and discontinued operations liabilities, respectively, and, the results of Gill Ranch are presented, net of tax, as discontinued operations separately from the results of continuing operations for all periods presented. The expenses included in the results of discontinued operations are the direct operating expenses incurred by Gill Ranch that may be reasonably segregated from the costs of NW Holdings' continuing operations. The following table presents the carrying amounts of the major components of Gill Ranch that are classified as discontinued operations assets and liabilities on the consolidated balance sheets: NW Holdings Discontinued Operations March 31, December 31, In thousands 2019 2018 2018 Assets: Accounts receivable $ 1,277 $ 193 $ 390 Inventories 627 736 685 Other current assets 337 583 333 Property, plant, and equipment 12,033 10,812 11,621 Less: Accumulated depreciation 7 4 7 Operating lease right of use asset 118 — — Other non-current assets 247 51 247 Discontinued operations - current assets (1) 14,632 1,512 13,269 Discontinued operations - non-current assets (1) — 10,859 — Total discontinued operations assets $ 14,632 $ 12,371 $ 13,269 Liabilities: Accounts payable $ 1,102 $ 462 $ 873 Taxes accrued 59 334 — Other current liabilities 300 413 307 Operating lease liabilities 111 — — Other non-current liabilities 11,710 11,979 11,779 Discontinued operations - current liabilities (1) 13,282 1,209 12,959 Discontinued operations - non-current liabilities (1) — 11,979 — Total discontinued operations liabilities $ 13,282 $ 13,188 $ 12,959 (1) The total assets and liabilities of Gill Ranch are classified as current as of March 31, 2019 and December 31, 2018 because it is probable that the sale will be completed within one year. The following table presents the operating results of Gill Ranch, which was reported within the gas storage segment historically, and is presented net of tax on the consolidated statements of comprehensive income: NW Holdings Discontinued Operations Three Months Ended March 31, In thousands, except per share data 2019 2018 Revenues $ 1,721 $ 1,077 Expenses: Operations and maintenance 1,613 1,036 General taxes 59 334 Depreciation and amortization 106 110 Other expenses and interest 237 241 Total expenses 2,015 1,721 Loss from discontinued operations before income taxes (294 ) (644 ) Income tax benefit (77 ) (170 ) Loss from discontinued operations, net of tax $ (217 ) $ (474 ) Loss from discontinued operations per share of common stock: Basic $ (0.01 ) $ (0.02 ) Diluted (0.01 ) (0.02 ) NW Natural As a result of the holding company reorganization in October 2018, NWN Energy, NWN Gas Storage, Gill Ranch, NNG Financial, NWN Water, and NW Holdings, which were direct and indirect subsidiaries of NW Natural prior to the reorganization, are no longer subsidiaries of NW Natural. As a result, NW Natural's financial statements reflect amounts related to these entities as discontinued operations for all periods presented. The expenses included in the results of discontinued operations are the direct operating expenses incurred by the entities that may be reasonably segregated from the costs of NW Natural's continuing operations. The following table presents the carrying amounts of the major components of NWN Energy, NWN Gas Storage, Gill Ranch, NNG Financial, NWN Water, and NW Holdings that are classified as discontinued operations assets and liabilities on NW Natural's consolidated balance sheets: NW Natural Discontinued Operations In thousands March 31, 2018 Assets: Cash $ 311 Accounts receivable 193 Receivables from affiliates 3,852 Inventories 736 Other current assets 639 Property, plant, and equipment 11,186 Less: Accumulated depreciation 203 Other investments 13,691 Other non-current assets 64 Discontinued operations - current assets 5,731 Discontinued operations - non-current assets 24,738 Total discontinued operations assets $ 30,469 Liabilities: Accounts payable $ 731 Taxes accrued 368 Payables to affiliates 660 Other current liabilities 401 Deferred tax liabilities (16,397 ) Other non-current liabilities 12,067 Discontinued operations - current liabilities 2,160 Discontinued operations - non-current liabilities (4,330 ) Total discontinued operations liabilities $ (2,170 ) The following table presents the operating results prior to the holding company reorganization effective October 1, 2018 of NWN Energy, NWN Gas Storage, Gill Ranch, NNG Financial, NWN Water, and NW Holdings, which were historically reported within the gas storage segment and other, and is presented net of tax on NW Natural's consolidated statements of comprehensive income: NW Natural Discontinued Operations Three Months Ended March 31, In thousands, except per share data 2018 Revenues $ 1,133 Expenses: Operations and maintenance 1,059 General taxes 347 Depreciation and amortization 117 Other expenses and interest 260 Total expenses 1,783 Loss from discontinued operations before income taxes (650 ) Income tax benefit (173 ) Loss from discontinued operations, net of tax $ (477 )
Northwest Natural Gas Company [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Groups, Including Discontinued Operations		The following table presents the operating results prior to the holding company reorganization effective October 1, 2018 of NWN Energy, NWN Gas Storage, Gill Ranch, NNG Financial, NWN Water, and NW Holdings, which were historically reported within the gas storage segment and other, and is presented net of tax on NW Natural's consolidated statements of comprehensive income: NW Natural Discontinued Operations Three Months Ended March 31, In thousands, except per share data 2018 Revenues $ 1,133 Expenses: Operations and maintenance 1,059 General taxes 347 Depreciation and amortization 117 Other expenses and interest 260 Total expenses 1,783 Loss from discontinued operations before income taxes (650 ) Income tax benefit (173 ) Loss from discontinued operations, net of tax $ (477 )
Northwest Holdings [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Groups, Including Discontinued Operations	The following table presents the operating results of Gill Ranch, which was reported within the gas storage segment historically, and is presented net of tax on the consolidated statements of comprehensive income: NW Holdings Discontinued Operations Three Months Ended March 31, In thousands, except per share data 2019 2018 Revenues $ 1,721 $ 1,077 Expenses: Operations and maintenance 1,613 1,036 General taxes 59 334 Depreciation and amortization 106 110 Other expenses and interest 237 241 Total expenses 2,015 1,721 Loss from discontinued operations before income taxes (294 ) (644 ) Income tax benefit (77 ) (170 ) Loss from discontinued operations, net of tax $ (217 ) $ (474 ) Loss from discontinued operations per share of common stock: Basic $ (0.01 ) $ (0.02 ) Diluted (0.01 ) (0.02 )
Northwest Natural Gas Company [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Groups, Including Discontinued Operations		The following table presents the carrying amounts of the major components of NWN Energy, NWN Gas Storage, Gill Ranch, NNG Financial, NWN Water, and NW Holdings that are classified as discontinued operations assets and liabilities on NW Natural's consolidated balance sheets: NW Natural Discontinued Operations In thousands March 31, 2018 Assets: Cash $ 311 Accounts receivable 193 Receivables from affiliates 3,852 Inventories 736 Other current assets 639 Property, plant, and equipment 11,186 Less: Accumulated depreciation 203 Other investments 13,691 Other non-current assets 64 Discontinued operations - current assets 5,731 Discontinued operations - non-current assets 24,738 Total discontinued operations assets $ 30,469 Liabilities: Accounts payable $ 731 Taxes accrued 368 Payables to affiliates 660 Other current liabilities 401 Deferred tax liabilities (16,397 ) Other non-current liabilities 12,067 Discontinued operations - current liabilities 2,160 Discontinued operations - non-current liabilities (4,330 ) Total discontinued operations liabilities $ (2,170 )
Northwest Holdings [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Groups, Including Discontinued Operations	The following table presents the carrying amounts of the major components of Gill Ranch that are classified as discontinued operations assets and liabilities on the consolidated balance sheets: NW Holdings Discontinued Operations March 31, December 31, In thousands 2019 2018 2018 Assets: Accounts receivable $ 1,277 $ 193 $ 390 Inventories 627 736 685 Other current assets 337 583 333 Property, plant, and equipment 12,033 10,812 11,621 Less: Accumulated depreciation 7 4 7 Operating lease right of use asset 118 — — Other non-current assets 247 51 247 Discontinued operations - current assets (1) 14,632 1,512 13,269 Discontinued operations - non-current assets (1) — 10,859 — Total discontinued operations assets $ 14,632 $ 12,371 $ 13,269 Liabilities: Accounts payable $ 1,102 $ 462 $ 873 Taxes accrued 59 334 — Other current liabilities 300 413 307 Operating lease liabilities 111 — — Other non-current liabilities 11,710 11,979 11,779 Discontinued operations - current liabilities (1) 13,282 1,209 12,959 Discontinued operations - non-current liabilities (1) — 11,979 — Total discontinued operations liabilities $ 13,282 $ 13,188 $ 12,959 (1) The total assets and liabilities of Gill Ranch are classified as current as of March 31, 2019 and December 31, 2018 because it is probable that the sale will be completed within one year.

Significant Accounting Polici_4

Significant Accounting Policies - Regulatory Asset Disclosure (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Regulatory Assets [Line Items]
Regulatory Assets, Current	$ 46,317	$ 41,930	$ 45,900
Regulatory Assets, Noncurrent	327,194	371,786	343,037
Northwest Natural Gas Company [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	46,317	41,930	45,900
Regulatory Assets, Noncurrent	327,194	371,786	343,037
Northwest Natural Gas Company [Member] | Deferred Derivative Gain (Loss) [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	2,845	12,381	17,569
Regulatory Assets, Noncurrent	1,161	3,025	2,355
Northwest Natural Gas Company [Member] | Gas costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	17,927	2,873	591
Regulatory Assets, Noncurrent	8,919	9,978	49
Northwest Natural Gas Company [Member] | Environmental costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	5,090	5,601	5,818
Regulatory Assets, Noncurrent	66,612	76,149	66,730
Northwest Natural Gas Company [Member] | Decoupling [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	3,937	9,140	9,578
Regulatory Assets, Noncurrent	250	2,545	2,663
Northwest Natural Gas Company [Member] | Pension balancing [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	4,955	0	0
Regulatory Assets, Noncurrent	50,408	74,173	63,940
Northwest Natural Gas Company [Member] | Income taxes [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	2,209	2,218	2,218
Regulatory Assets, Noncurrent	17,758	19,185	19,267
Northwest Natural Gas Company [Member] | Pension and other postretirement benefit liabilities [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Noncurrent	171,565	174,993	175,505
Northwest Natural Gas Company [Member] | Other [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	9,354	9,717	10,126
Regulatory Assets, Noncurrent	$ 10,521	$ 11,738	$ 12,528

Significant Accounting Polici_5

Significant Accounting Policies - Regulatory Liability Disclosure (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	$ 46,770	$ 47,436	$ 34,946
Regulatory Liability, Noncurrent	600,698	611,560	600,442
Northwest Natural Gas Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	46,770	47,436	34,946
Regulatory Liability, Noncurrent	600,698	611,560	600,442
Northwest Natural Gas Company [Member] | Gas costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	11,126	17,182	17,798
Regulatory Liability, Noncurrent	1,421	552	5,639
Northwest Natural Gas Company [Member] | Deferred Derivative Gain (Loss) [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	7,284	8,740	1,120
Regulatory Liability, Noncurrent	541	725	1,148
Northwest Natural Gas Company [Member] | Decoupling [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	2,055	2,264	2,501
Regulatory Liability, Noncurrent	614	0	1,253
Northwest Natural Gas Company [Member] | Income taxes [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	7,763	0	0
Regulatory Liability, Noncurrent	202,692	225,408	219,795
Northwest Natural Gas Company [Member] | Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	18,542	19,250	13,527
Regulatory Liability, Noncurrent	10,728	4,411	7,244
Northwest Natural Gas Company [Member] | Accrued asset removal costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Noncurrent	$ 384,700	$ 380,500	$ 365,400

Significant Accounting Polici_6

Significant Accounting Policies - Leases ASU 2016-02 (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right of use asset	$ 6,163,000	$ 0	$ 0
Operating Lease, Liability	6,151,000
Property, plant, and equipment	3,439,460,000	3,414,490,000	3,251,075,000
Other Liabilities, Noncurrent	120,569,000	147,763,000	137,147,000
Northwest Natural Gas Company [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right of use asset	5,903,000	0	0
Operating Lease, Liability	5,890,000
Property, plant, and equipment	3,435,304,000	3,410,439,000	3,250,700,000
Other Liabilities, Noncurrent	120,465,000	147,668,000	$ 137,059,000
Accounting Standards Update 2016-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	0
Initial Direct or Capitalized Lease Cost to be De-recognized, Legacy Leases	0
Operating lease right of use asset	7,300,000
Operating Lease, Liability	7,300,000
Accounting Standards Update 2016-02 [Member] | Northwest Natural Gas Company [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right of use asset	7,000,000
Operating Lease, Liability	$ 7,000,000
Accounting Standards Update 2016-02 [Member] | New Headquarters Lease [Member] | Build to Suit Lease [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Property, plant, and equipment		26,000,000
Other Liabilities, Noncurrent		$ 26,000,000

Significant Accounting Polici_7

Significant Accounting Policies Significant Accounting Policies - AOCI Tax Effects ASU 2018-02 (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stranded Deferred Tax Remeasurement Benefit	$ 1,366	$ 0
Accounting Standards Update 2018-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stranded Deferred Tax Remeasurement Benefit	$ 1,400

Earnings Per Share (Details)

Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement [Line Items]
Net income from continuing operations	$ 43,418	$ 42,011
Loss from discontinued operations, net of tax	(217)	(474)
Net income	$ 43,201	$ 41,537
Average common shares outstanding:
Average common shares outstanding - basic (in shares)	28,906	28,753
Additional shares for stock-based compensation plans	64	50
Average common shares outstanding - diluted (in shares)	28,970	28,803
Earnings from continuing operations per share of common stock:
Basic (in dollars per share)	$ 1.50	$ 1.46
Diluted (in dollars per share)	1.50	1.46
Earnings (loss) per share of common stock
Basic (in dollars per share)	1.49	1.44
Diluted (in dollars per share)	$ 1.49	$ 1.44
Antidilutive shares	5	16
Discontinued Operations, Held-for-sale [Member] | Gill Ranch [Member]
Income Statement [Line Items]
Loss from discontinued operations, net of tax	$ (217)	$ (474)
Loss from discontinued operations per share of common stock:
Basic (in dollars per share)	$ (0.01)	$ (0.02)
Diluted (in dollars per share)	$ (0.01)	$ (0.02)

Segment Information - Narrative

Segment Information - Narrative (Details)	3 Months Ended
	Mar. 31, 2019
Operating Segments [Member]
Segment Reporting Information [Line Items]
Number of Reportable Segments	1
Oregon [Member] | Northwest Holdings and Northwest Natural [Member] | Natural Gas Distribution [Member]
Segment Reporting Information [Line Items]
Percent Of Pre Tax Income From Gas Storage Retained When The Costs Of The Capacity Are Not In Utility Rates	80.00%
Percent Of Pre Tax Income From Gas Storage Retained When The Costs Of The Capacity Are In Utility Rates	10.00%
Percent Of Pre Tax Income From Gas Storage Credited To Deferred Regulatory Account	20.00%
Percent Of Pre Tax Income From Gas Storage Credited To Deferred Regulatory Account When In Rates	90.00%

Segment Information - Schedule

Segment Information - Schedule of Summarized Financial Information by Segment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Segment Reporting Information [Line Items]
Operating revenues	$ 285,348	$ 263,635
Depreciation and amortization	21,572	20,875
Income from operations	76,045	67,751
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	43,418	42,011
Capital expenditures	48,764	57,329
Total assets	3,191,117	3,029,339	$ 3,242,662
Discontinued operations - current assets	14,632	1,512	13,269
Discontinued operations - total assets		12,400
Natural Gas Distribution [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	279,041	257,933
Depreciation and amortization	21,249	20,543
Income from operations	72,898	64,756
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	41,206	39,883
Capital expenditures	48,606	56,894
Total assets	3,091,062	2,952,294	3,141,969
Other Northwest Natural [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating revenues	5,805	5,702
Depreciation and amortization	255	325
Income from operations	3,746	2,982
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	2,689	2,131
Capital expenditures	52	435
Total assets	49,566	50,850	50,767
Northwest Natural Gas Company [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	284,846	263,635
Depreciation and amortization	21,504	20,868
Income from operations	76,644	67,738
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	43,895	42,014
Capital expenditures	48,658	57,329
Total assets	3,140,628	3,003,144	3,192,736
Other Northwest Holdings [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating revenues	502	0
Depreciation and amortization	68	7
Income from operations	(599)	13
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	(477)	(3)
Capital expenditures	106	0
Total assets	35,857	13,824	36,657
Northwest Natural Gas Company [Member]
Segment Reporting Information [Line Items]
Operating revenues	284,846	263,635
Depreciation and amortization	21,504	20,868
Income from operations	76,644	67,738
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	43,895	42,014
Capital expenditures	48,658	57,329
Total assets	3,140,628	3,033,613	3,192,736
Discontinued operations - current assets	0	5,731	0
Discontinued operations - total assets	0	4,330	0
Northwest Natural Gas Company [Member] | Natural Gas Distribution [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	279,041	257,933
Northwest Natural Gas Company [Member] | Other Northwest Natural [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating revenues	5,805	5,702
Northwest Natural Gas Company [Member] | Northwest Natural Gas Company [Member]
Segment Reporting Information [Line Items]
Operating revenues	284,846	263,635
Northwest Natural Gas Company [Member]
Segment Reporting Information [Line Items]
Discontinued operations - total assets		30,500
Parent Company [Member]
Segment Reporting Information [Line Items]
Operating revenues	285,348	263,635
Depreciation and amortization	21,572	20,875
Income from operations	76,045	67,751
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	43,418	42,011
Capital expenditures	48,764	57,329
Total assets	$ 3,176,485	$ 3,016,968	$ 3,229,393

Segment Information - Additiona

Segment Information - Additional Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Segment Reporting Information [Line Items]
Operating revenues	$ 285,348	$ 263,635
Cost of gas	105,457	108,106
Environmental remediation	8,947	4,624
Operating Segments [Member] | Natural Gas Distribution [Member]
Segment Reporting Information [Line Items]
Operating revenues	279,041	257,933
Cost of gas	105,513	108,164
Environmental remediation	8,947	4,624
Revenue taxes	11,926	12,429
NGD margin	$ 152,655	$ 132,716

Leases - Lease Revenue (Details

Leases - Lease Revenue (Details)	3 Months Ended
	Mar. 31, 2019USD ($)
Lease Revenue [Abstract]
Residual Value of Leased Asset	$ 0
Variable Lease, Payment	0
Operating leases	48,000
Sales-type leases	60,000
Total lease revenue	108,000
Operating Leases Payment to be Received [Abstract]
Operating Lease, Payments to be Received, Remainder of Fiscal Year	94,000
Operating Lease, Payments to be Received, Two Years	61,000
Operating Lease, Payments to be Received, Three Years	49,000
Operating Lease, Payments to be Received, Four Years	45,000
Operating Lease, Payments to be Received, Five Years	45,000
Operating Lease, Payments to be Received, Thereafter	138,000
Total lease revenue	432,000
Total Lease Payments to be Received [Abstract]
Lease Payments to be Received, Remainder of Fiscal Year	380,000
Lease Payments to be Received, Two Years	273,000
Lease Payments to be Received, Three Years	247,000
Lease Payments to be Received, Four Years	231,000
Lease Payments to be Received, Five Years	218,000
Lease Payments to be Received, Thereafter	616,000
Total lease revenue	1,965,000
Sales-type Lease [Member]
Sales-type Leases Payments to be Received [Abstract]
Sales-type Lease, Payments to be Received, Remainder of Fiscal Year	286,000
Sales-type Lease, Payments to be Received, Two Years	212,000
Sales-type Lease, Payments to be Received, Three Years	198,000
Sales-type Lease, Payments to be Received, Four Years	186,000
Sales-type Lease, Payments to be Received, Five Years	173,000
Sales-type Lease, Payments to be Received, Thereafter	478,000
Total lease revenue	1,533,000
Less: imputed interest	459,000
Total lease receivable	$ 1,074,000

Revenue - Disaggregation of Rev

Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	$ 302,493	$ 263,931
Revenues	285,348	263,635
Operating leases	48
Natural Gas Sales [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	296,186	258,229
Gas Storage Revenue, Net of Regulatory Sharing [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	2,783	2,577
Asset Management Revenue, Net of Regulatory Sharing [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,506	1,579
Appliance Center Revenue [Member] | Transferred at Point in Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,516	1,546
Other revenue [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	502	0
Alternative revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	(17,253)	(372)
Leasing revenue [Member]
Disaggregation of Revenue [Line Items]
Operating leases	108	76
Northwest Natural Gas Company [Member]
Disaggregation of Revenue [Line Items]
Revenues	284,846	263,635
Northwest Natural Gas Company [Member] | Northwest Natural Gas Company [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	301,991	263,931
Revenues	284,846	263,635
Northwest Natural Gas Company [Member] | Northwest Natural Gas Company [Member] | Natural Gas Sales [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	296,186	258,229
Northwest Natural Gas Company [Member] | Northwest Natural Gas Company [Member] | Gas Storage Revenue, Net of Regulatory Sharing [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	2,783	2,577
Northwest Natural Gas Company [Member] | Northwest Natural Gas Company [Member] | Asset Management Revenue, Net of Regulatory Sharing [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,506	1,579
Northwest Natural Gas Company [Member] | Northwest Natural Gas Company [Member] | Appliance Center Revenue [Member] | Transferred at Point in Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,516	1,546
Northwest Natural Gas Company [Member] | Northwest Natural Gas Company [Member] | Other revenue [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0
Northwest Natural Gas Company [Member] | Northwest Natural Gas Company [Member] | Alternative revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	(17,253)	(372)
Northwest Natural Gas Company [Member] | Northwest Natural Gas Company [Member] | Leasing revenue [Member]
Disaggregation of Revenue [Line Items]
Operating leases	108	76
Operating Segments [Member] | Natural Gas Distribution [Member]
Disaggregation of Revenue [Line Items]
Revenues	279,041	257,933
Operating Segments [Member] | Natural Gas Distribution [Member] | Northwest Natural Gas Company [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	296,186	258,229
Revenues	279,041	257,933
Operating Segments [Member] | Natural Gas Distribution [Member] | Northwest Natural Gas Company [Member] | Natural Gas Sales [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	296,186	258,229
Operating Segments [Member] | Natural Gas Distribution [Member] | Northwest Natural Gas Company [Member] | Gas Storage Revenue, Net of Regulatory Sharing [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0
Operating Segments [Member] | Natural Gas Distribution [Member] | Northwest Natural Gas Company [Member] | Asset Management Revenue, Net of Regulatory Sharing [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0
Operating Segments [Member] | Natural Gas Distribution [Member] | Northwest Natural Gas Company [Member] | Appliance Center Revenue [Member] | Transferred at Point in Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0
Operating Segments [Member] | Natural Gas Distribution [Member] | Northwest Natural Gas Company [Member] | Other revenue [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0
Operating Segments [Member] | Natural Gas Distribution [Member] | Northwest Natural Gas Company [Member] | Alternative revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	(17,253)	(372)
Operating Segments [Member] | Natural Gas Distribution [Member] | Northwest Natural Gas Company [Member] | Leasing revenue [Member]
Disaggregation of Revenue [Line Items]
Operating leases	108	76
Operating Segments [Member] | Northwest Natural Gas Company [Member]
Disaggregation of Revenue [Line Items]
Revenues	284,846	263,635
Corporate, Non-Segment [Member] | Other Northwest Natural [Member]
Disaggregation of Revenue [Line Items]
Revenues	5,805	5,702
Corporate, Non-Segment [Member] | Other Northwest Natural [Member] | Northwest Natural Gas Company [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	5,805	5,702
Revenues	5,805	5,702
Corporate, Non-Segment [Member] | Other Northwest Natural [Member] | Northwest Natural Gas Company [Member] | Natural Gas Sales [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0
Corporate, Non-Segment [Member] | Other Northwest Natural [Member] | Northwest Natural Gas Company [Member] | Gas Storage Revenue, Net of Regulatory Sharing [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	2,783	2,577
Corporate, Non-Segment [Member] | Other Northwest Natural [Member] | Northwest Natural Gas Company [Member] | Asset Management Revenue, Net of Regulatory Sharing [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,506	1,579
Corporate, Non-Segment [Member] | Other Northwest Natural [Member] | Northwest Natural Gas Company [Member] | Appliance Center Revenue [Member] | Transferred at Point in Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,516	1,546
Corporate, Non-Segment [Member] | Other Northwest Natural [Member] | Northwest Natural Gas Company [Member] | Other revenue [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0
Corporate, Non-Segment [Member] | Other Northwest Natural [Member] | Northwest Natural Gas Company [Member] | Alternative revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	0	0
Corporate, Non-Segment [Member] | Other Northwest Natural [Member] | Northwest Natural Gas Company [Member] | Leasing revenue [Member]
Disaggregation of Revenue [Line Items]
Operating leases	0	0
Corporate, Non-Segment [Member] | Other Northwest Holdings [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	502	0
Revenues	502	0
Corporate, Non-Segment [Member] | Other Northwest Holdings [Member] | Natural Gas Sales [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0
Corporate, Non-Segment [Member] | Other Northwest Holdings [Member] | Gas Storage Revenue, Net of Regulatory Sharing [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0
Corporate, Non-Segment [Member] | Other Northwest Holdings [Member] | Asset Management Revenue, Net of Regulatory Sharing [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0
Corporate, Non-Segment [Member] | Other Northwest Holdings [Member] | Appliance Center Revenue [Member] | Transferred at Point in Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0
Corporate, Non-Segment [Member] | Other Northwest Holdings [Member] | Other revenue [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	502	0
Corporate, Non-Segment [Member] | Other Northwest Holdings [Member] | Alternative revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	0	0
Corporate, Non-Segment [Member] | Other Northwest Holdings [Member] | Leasing revenue [Member]
Disaggregation of Revenue [Line Items]
Operating leases	$ 0	$ 0

Leases - Lease Expense (Details

Leases - Lease Expense (Details)	3 Months Ended
	Mar. 31, 2019USD ($)
Lessee, Lease, Description [Line Items]
Residual Value of Leased Asset	$ 0
Lease Expense [Abstract]
Operating Lease, Expense	1,188,000
Short-term Lease, Cost	$ 160,000
Minimum [Member]
Operating Lease Terms [Abstract]
Lessee, Operating Lease, Term of Contract	1 year
Maximum [Member]
Operating Lease Terms [Abstract]
Lessee, Operating Lease, Term of Contract	11 years
Northwest Natural Gas Company [Member]
Lease Expense [Abstract]
Operating Lease, Expense	$ 1,142,000
Short-term Lease, Cost	160,000
Other Northwest Holdings [Member] | Corporate, Non-Segment [Member]
Lease Expense [Abstract]
Operating Lease, Expense	46,000
Short-term Lease, Cost	$ 0

Revenue - Revenue, Remaining Pe

Revenue - Revenue, Remaining Performance Obligation (Details) $ in Millions	Mar. 31, 2019USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Year	2019
Revenue, Remaining Performance Obligation, Amount	$ 10.2
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Year	2020
Revenue, Remaining Performance Obligation, Amount	$ 11.7
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Year	2021
Revenue, Remaining Performance Obligation, Amount	$ 10.7
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Year	2022
Revenue, Remaining Performance Obligation, Amount	$ 7
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Year	2023
Revenue, Remaining Performance Obligation, Amount	$ 6.8
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 52.2

Leases - Lease Asset and Liabil

Leases - Lease Asset and Liabilities (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Mar. 31, 2018USD ($)
Operating Lease Asset and Liabilities [Abstract]
Operating lease right of use asset	$ 6,163	$ 0			$ 0
Operating lease liabilities current liabilities	4,656	0			0
Operating lease liabilities noncurrent liabilities	1,495	0			0
Total operating lease liabilities	6,151
Maturity of Operating Lease Liabilities [Abstract]
Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year	3,601
Lessee, Operating Lease, Liability, Payments, Due Year Two	2,082
Lessee, Operating Lease, Liability, Payments, Due Year Three	129
Lessee, Operating Lease, Liability, Payments, Due Year Four	93
Lessee, Operating Lease, Liability, Payments, Due Year Five	71
Lessee, Operating Lease, Liability, Payments, Due after Year Five	497
Lessee, Operating Lease, Liability, Payments, Due	6,473
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	322
Total operating lease liabilities	6,151
Operating lease liabilities current liabilities	4,656	0			0
Operating lease liabilities noncurrent liabilities	1,495	0			0
Lease Not Yet Commenced [Abstract]
Lessee, Operating Lease, Liability, Payments, Due	6,473
Leases Cash Flow [Abstract]
Operating cash flows from operating leases	1,134
Operating leases	7,291
Finance Leases [Abstract]
Finance Lease, Right-of-Use Asset	200
Prior Period Disclosures [Abstract]
Operating Leases, Rent Expense		5,900	$ 7,300	$ 5,900
Other Northwest Holdings [Member] | Corporate, Non-Segment [Member]
Operating Lease Asset and Liabilities [Abstract]
Operating lease right of use asset	260
Operating lease liabilities current liabilities	179
Operating lease liabilities noncurrent liabilities	82
Total operating lease liabilities	261
Maturity of Operating Lease Liabilities [Abstract]
Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year	139
Lessee, Operating Lease, Liability, Payments, Due Year Two	102
Lessee, Operating Lease, Liability, Payments, Due Year Three	28
Lessee, Operating Lease, Liability, Payments, Due Year Four	0
Lessee, Operating Lease, Liability, Payments, Due Year Five	0
Lessee, Operating Lease, Liability, Payments, Due after Year Five	0
Lessee, Operating Lease, Liability, Payments, Due	269
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	8
Total operating lease liabilities	261
Operating lease liabilities current liabilities	179
Operating lease liabilities noncurrent liabilities	82
Lease Not Yet Commenced [Abstract]
Lessee, Operating Lease, Liability, Payments, Due	269
Leases Cash Flow [Abstract]
Operating cash flows from operating leases	43
Operating leases	304
Northwest Natural Gas Company [Member]
Operating Lease Asset and Liabilities [Abstract]
Operating lease right of use asset	5,903	0			0
Operating lease liabilities current liabilities	4,477	0			0
Operating lease liabilities noncurrent liabilities	1,413	0			0
Total operating lease liabilities	$ 5,890
Operating Lease, Weighted Average Remaining Lease Term	1 year 4 months
Operating Lease, Weighted Average Discount Rate, Percent	3.79%
Maturity of Operating Lease Liabilities [Abstract]
Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year	$ 3,462
Lessee, Operating Lease, Liability, Payments, Due Next Twelve Months		5,368
Lessee, Operating Lease, Liability, Payments, Due Year Two	1,980	4,812
Lessee, Operating Lease, Liability, Payments, Due Year Three	101	7,077
Lessee, Operating Lease, Liability, Payments, Due Year Four	93	7,223
Lessee, Operating Lease, Liability, Payments, Due Year Five	71	7,304
Lessee, Operating Lease, Liability, Payments, Due after Year Five	497	149,881
Lessee, Operating Lease, Liability, Payments, Due	6,204	181,665
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	314
Total operating lease liabilities	5,890
Operating lease liabilities current liabilities	4,477	0			0
Operating lease liabilities noncurrent liabilities	1,413	0			$ 0
Lease Not Yet Commenced [Abstract]
Lessee, Operating Lease, Liability, Payments, Due	6,204	$ 181,665
Leases Cash Flow [Abstract]
Operating cash flows from operating leases	1,091
Operating leases	6,987
New Headquarters Lease [Member]
Maturity of Operating Lease Liabilities [Abstract]
Lessee, Operating Lease, Liability, Payments, Due	$ 160,000
Lease Not Yet Commenced [Abstract]
Operating Lease, Lease Not yet Commenced, Number of Renewal Terms	2
Lessee, Operating Lease, Lease Not yet Commenced, Term of Contract	20 years
Lessee, Operating Lease, Lease Not yet Commenced, Renewal Term	7 years
Lessee, Operating Lease, Liability, Payments, Due	$ 160,000

Stock-Based Compensation (Detai

Stock-Based Compensation (Details) - Long Term Incentive Plan $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)$ / sharesshares
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares granted (in shares)	0
Award vesting period	3 years
Unrecognized compensation costs | $	$ 800
Performance Shares | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Conversion ratio, percent of target	0.00%
Performance Shares | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Conversion ratio, percent of target	200.00%
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	4 years
Number of RSUs granted in period (in shares)	28,884
Weighted-average grant date fair value (in dollars per share) | $ / shares	$ 64.26
Unrecognized compensation costs | $	$ 4,000
Unrecognized Compensation Cost, Period for Recognition	through 2023
A 2018 Award and 2019 Award [Member] | Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense | $	$ 0
Target Achieved [Member] | A 2018 Award [Member] | Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share Based Compensation Award Target Share	33,163
Target Achieved [Member] | A 2019 Award [Member] | Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share Based Compensation Award Target Share	36,250

Debt Short-term Debt (Details)

Debt Short-term Debt (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Short-term Debt [Abstract]
Short-term debt	$ 176,391	$ 217,620	$ 50,000
Short-term Debt Maximum Remaining Maturity	33 days
Short-term Debt Average Remaining Maturity	17 days

Long-Term Debt (Details)

Long-Term Debt (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019USD ($)
Debt Instrument [Line Items]
Long-term Debt	$ 736.6
Maturity start date range	Jan. 1, 2019
Maturity end date range	Dec. 31, 2048
Weighted average interest rate	5.009%
Minimum [Member]
Debt Instrument [Line Items]
Stated interest rate	2.822%
Maximum [Member]
Debt Instrument [Line Items]
Stated interest rate	9.05%

Debt Fair Value of Long Term De

Debt Fair Value of Long Term Debt (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Debt Instrument [Line Items]
Carrying amount	$ 736,600
Northwest Natural Gas Company [Member]
Debt Instrument [Line Items]
Gross long-term debt	739,700	$ 739,700	$ 764,700
Unamortized debt issuance costs	(5,246)	(5,577)	(6,418)
Carrying amount	734,454	734,123	758,282
Estimated fair value	$ 775,590	$ 760,222	$ 807,288

Pension and Other Postretirem_3

Pension and Other Postretirement Benefit Costs - Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 1,517	$ 1,807
Interest cost	4,662	4,183
Expected return on plan assets	(5,207)	(5,151)
Amortization of net actuarial loss	2	11
Defined Benefit Plan, Amortization of Gain (Loss)	3,603	4,523
Net periodic benefit cost	4,577	5,373
Amount allocated to construction	(586)	(682)
Amount deferred to regulatory balancing account(1)	0	(2,756)
Defined Benefit Plan Net Periodic Benefit Cost Charged To Expense	3,991	1,935
Regulatory Pension Disallowance	10,500	0
Amortization of Regulatory Balancing Account	12,511	0
Net amount charged to expense	27,002	1,935
Other Postretirement Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	68	80
Interest cost	281	241
Expected return on plan assets	0	0
Amortization of net actuarial loss	(117)	(117)
Defined Benefit Plan, Amortization of Gain (Loss)	97	110
Net periodic benefit cost	329	314
Amount allocated to construction	(24)	(27)
Amount deferred to regulatory balancing account(1)	0	0
Defined Benefit Plan Net Periodic Benefit Cost Charged To Expense	305	287
Regulatory Pension Disallowance	0	0
Amortization of Regulatory Balancing Account	0	0
Net amount charged to expense	$ 305	$ 287

Pension and Other Postretirem_4

Pension and Other Postretirement Benefit Costs - Amounts Recognized in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss) [Abstract]
Beginning balance	$ (7,188)	$ (8,438)
Amortization of actuarial losses	156	209
Stranded Deferred Tax Remeasurement Benefit	(1,366)	0
Total reclassifications before tax	(1,210)	209
Tax (benefit) expense	(41)	(55)
Total reclassifications for the period	(1,251)	154
Ending balance	$ (8,439)	$ (8,284)

Pension and Other Postretirem_5

Pension and Other Postretirement Benefit Costs - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Pension and Other Postretirement Benefits Cost (Reversal of Cost) [Abstract]
Defined benefit pension plan cash contributions	$ 1,500
Estimated future employer contributions in next fiscal year	9,500
Employer contributions	$ 2,100	$ 2,000

Income Tax (Details)

Income Tax (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Income taxes at statutory rates (federal and state)	$ 14,313	$ 15,368
Differences required to be flowed-through by regulatory commissions	(5,260)	849
Other, net	(378)	(585)
Total provision for income taxes on continuing operations	$ 8,675	$ 15,632
Effective tax rate for continuing operations	16.70%	27.10%
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%		35.00%
Northwest Natural Gas Company [Member]
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Income taxes at statutory rates (federal and state)	$ 14,485	$ 15,372
Differences required to be flowed-through by regulatory commissions	(5,260)	849
Other, net	(377)	(586)
Total provision for income taxes on continuing operations	$ 8,848	$ 15,635
Effective tax rate for continuing operations	16.80%	27.10%

Property, Plant and Equipment_3

Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Property, Plant and Equipment [Line Items]
Property, plant, and equipment	$ 3,439,460	$ 3,414,490	$ 3,251,075
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	1,005,117	993,118	972,773
Property, Plant and Equipment, Net	2,434,343	2,421,372	2,278,302
Other Liabilities, Noncurrent	120,569	147,763	137,147
Natural Gas Distribution [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment	3,159,754	3,134,122	3,003,962
Public Utilities, Property, Plant and Equipment, Construction Work in Progress	204,938	204,978	177,133
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	985,961	974,252	954,858
Property, Plant and Equipment, Net	2,378,731	2,364,848	2,226,237
Other Northwest Natural [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment	65,283	66,009	65,353
Public Utilities, Property, Plant and Equipment, Construction Work in Progress	5,329	5,330	4,252
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	18,851	18,603	17,715
Property, Plant and Equipment, Net	51,761	52,736	51,890
Northwest Natural Gas Company [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Net	2,430,492	2,417,584	2,278,127
Other Northwest Holdings [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment	4,156	4,051	375
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	305	263	200
Property, Plant and Equipment, Net	3,851	3,788	175
Northwest Holdings and Northwest Natural [Member]
Property, Plant and Equipment [Line Items]
Property, Plant, Equipment non-cash	$ 25,035	23,676	$ 21,855
New Headquarters Lease [Member]
Property, Plant and Equipment [Line Items]
Lessee, Operating Lease, Lease Not yet Commenced, Term of Contract	20 years
New Headquarters Lease [Member] | Accounting Standards Update 2016-02 [Member] | Build to Suit Lease [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment		26,000
Other Liabilities, Noncurrent		$ 26,000

Gas Reserves (Details)

Gas Reserves (Details)	3 Months Ended
	Mar. 31, 2019USD ($)
Reserve Quantities [Line Items]
Total cumulative gas reserves investment	$ 188,000,000
Term of hedge rate	10 years
Encana Oil & Gas (USA) Inc.
Reserve Quantities [Line Items]
Gas reserves investment	$ 178,000,000
Jonah Energy LLC
Reserve Quantities [Line Items]
Gas reserves investment	10,000,000
Additional rate per therm	$ 0.4725

Gas Reserves - Investment (Deta

Gas Reserves - Investment (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Reserve Quantities [Line Items]
Gas reserves	$ 16,157	$ 16,647	$ 15,124
Gas reserves, non-current	171,150	170,660	172,412
Less: Accumulated amortization	109,243	104,463	91,852
Total gas reserves	78,064	82,844	95,684
Less: Deferred taxes on gas reserves	19,638	20,071	22,115
Net investment in gas reserves	58,426	62,773	73,569
Jonah Energy LLC
Reserve Quantities [Line Items]
Total Gas Reserves Investment	$ 4,500	$ 4,800	$ 5,600

Investments (Details)

Investments (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Schedule of Equity Method Investments [Line Items]
Investment balance in TWH	$ 13.4	$ 13.4	$ 13.4
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	$ 13.4	$ 13.4	$ 13.4
Northwest Holdings [Member]
Schedule of Equity Method Investments [Line Items]
Ownership percentage of TWH	50.00%
TransCanada American Investments Ltd. [Member]
Schedule of Equity Method Investments [Line Items]
Ownership percentage of TWH	50.00%

Business Combinations Busines_2

Business Combinations Business Combinations (Details)	3 Months Ended		12 Months Ended
	Mar. 31, 2019USD ($)	Mar. 31, 2018USD ($)shares	Dec. 31, 2018USD ($)
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	$ 8,954,000	$ 0	$ 8,954,000
Goodwill, Impairment Loss	0
Falls Water Co [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred		$ 8,500,000
Business Combination, Consideration Transferred, Shares | shares		125,000
Business Acquisition, Connections of Acquired Business			5300
Goodwill			$ 6,400,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill	$ 0
Other insignificant acquisitions [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred			$ 2,800,000
Number of Businesses Acquired			3

Derivative Instruments Notional

Derivative Instruments Notional Amounts (Details) - Northwest Natural Gas Company [Member] therm in Thousands, $ in Thousands	Mar. 31, 2019USD ($)therm	Dec. 31, 2018USD ($)therm	Mar. 31, 2018USD ($)therm
Financial [Member] | Gas Year 2018 - 2019 [Member]
Derivative [Line Items]
TargetHedgeAchieved	48.00%
Financial [Member] | Gas Year 2017 - 2018 [Member]
Derivative [Line Items]
TargetHedgeAchieved	49.00%
Physical [Member] | Gas Year 2018 - 2019 [Member]
Derivative [Line Items]
TargetHedgeAchieved	24.00%
Physical [Member] | Gas Year 2017 - 2018 [Member]
Derivative [Line Items]
TargetHedgeAchieved	26.00%
Natural Gas Therms [Member] | Financial [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	255,550	408,850	326,080
Natural Gas Therms [Member] | Physical [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	422,825	472,275	420,200
Foreign Exchange Contract [Member]
Derivative [Line Items]
Foreign exchange | $	$ 7,241	$ 6,936	$ 7,611

Derivative Instruments Fair Val

Derivative Instruments Fair Value (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Derivative [Line Items]
Derivative, Fair Value, Net	$ 4.4	$ (5.7)	$ (17.7)

Unrealized and Realized Gain_Lo

Unrealized and Realized Gain/Loss (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Financial [Member]
Derivative [Line Items]
Derivative, Gain on Derivative	$ 11,300
Derivative, Loss on Derivative		$ (9,000)
Northwest Holdings and Northwest Natural [Member] | Natural gas commodity
Derivative [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	345	(79)
Northwest Holdings and Northwest Natural [Member] | Foreign exchange
Derivative [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	0	0
Northwest Holdings and Northwest Natural [Member] | Benefit (expense) to cost of gas | Natural gas commodity
Derivative [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	7,007	5,747
Northwest Holdings and Northwest Natural [Member] | Benefit (expense) to cost of gas | Foreign exchange
Derivative [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	(89)	(154)
Northwest Holdings and Northwest Natural [Member] | Sales [Member] | Natural gas commodity
Derivative [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	2,367	(227)
Northwest Holdings and Northwest Natural [Member] | Sales [Member] | Foreign exchange
Derivative [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	0	0
Deferred Derivative Gain (Loss) [Member] | Northwest Holdings and Northwest Natural [Member] | Natural gas commodity
Derivative [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	(9,029)	5,895
Deferred Derivative Gain (Loss) [Member] | Northwest Holdings and Northwest Natural [Member] | Foreign exchange
Derivative [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	$ 89	$ 154

Derivative Instruments Credit R

Derivative Instruments Credit Rating (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Derivative [Line Items]
Unrealized losses on derivatives	$ 500,000
Collateral Posted with NW Natural Counterparties [Member]
Derivative [Line Items]
Additional Collateral, Aggregate Fair Value	0	$ 0
Northwest Natural Gas Company [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	6,400,000	3,600,000	$ 2,200,000
Derivative liability	2,000,000	$ 9,300,000	$ 19,900,000
Northwest Natural Gas Company [Member] | (Current Ratings) A/A3
Derivative [Line Items]
With Adequate Assurance Calls	0
Without Adequate Assurance Calls	0
Northwest Natural Gas Company [Member] | BBB/Baa1
Derivative [Line Items]
With Adequate Assurance Calls	0
Without Adequate Assurance Calls	0
Northwest Natural Gas Company [Member] | BBB/Baa2
Derivative [Line Items]
With Adequate Assurance Calls	0
Without Adequate Assurance Calls	0
Northwest Natural Gas Company [Member] | BBB-/Baa3
Derivative [Line Items]
With Adequate Assurance Calls	0
Without Adequate Assurance Calls	0
Northwest Natural Gas Company [Member] | Speculative
Derivative [Line Items]
With Adequate Assurance Calls	604,000
Without Adequate Assurance Calls	$ 185,000

Environmental Matters (Details)

Environmental Matters (Details)	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Oregon [Member]
Site Contingency [Line Items]
Remediation Recovery Percentage	96.68%	96.68%	96.68%

Environmental Matters - Environ

Environmental Matters - Environmental Sites (Details) $ in Thousands	1 Months Ended			3 Months Ended
	Jul. 31, 2017USD ($)	Jan. 31, 2017USD ($)	May 31, 2012USD ($)	Mar. 31, 2019USD ($)propertyparty	Dec. 31, 2018USD ($)	Mar. 31, 2018USD ($)
Site Contingency [Line Items]
Current Liabilities				$ 30,143	$ 33,112	$ 16,763
Non-Current Liabilities				94,364	95,636	106,611
Gasco/Siltronic Sediments
Site Contingency [Line Items]
Current Liabilities				4,595	5,117	2,797
Non-Current Liabilities				44,427	44,351	45,015
Site Contingency, Environmental Remediation Costs Recognized				49,000
Gasco/Siltronic Sediments | Minimum [Member]
Site Contingency [Line Items]
Environmental Exit Costs, Anticipated Cost			$ 49,000
Gasco/Siltronic Sediments | Maximum [Member]
Site Contingency [Line Items]
Environmental Exit Costs, Anticipated Cost			$ 350,000
Portland Harbor Other [Member]
Site Contingency [Line Items]
Current Liabilities				2,299	2,600	1,769
Non-Current Liabilities				5,958	6,273	3,928
Gasco/Siltronic Upland [Member]
Site Contingency [Line Items]
Current Liabilities				11,951	13,983	11,408
Non-Current Liabilities				43,800	44,830	46,769
Central Service Center [Member]
Site Contingency [Line Items]
Current Liabilities				10	10	25
Non-Current Liabilities				0	0	0
Front Street [Member]
Site Contingency [Line Items]
Current Liabilities				11,288	11,402	764
Non-Current Liabilities				0	3	10,720
Undiscounted environmental remediation expense	$ 10,500
Additional studies and design costs	$ 800
Oregon Steel Mills [Member]
Site Contingency [Line Items]
Current Liabilities				0	0	0
Non-Current Liabilities				$ 179	$ 179	$ 179
Portland Harbor [Member]
Site Contingency [Line Items]
Number of potentially responsible parties (more than) | party				100
EPA final feasibility study and proposed remediation plan, clean-up costs, portland harbor		$ 1,050,000
Number of remediation projects | property				2
Portland Harbor [Member] | Minimum [Member]
Site Contingency [Line Items]
Percentage of clean-up costs		(30.00%)
Portland Harbor [Member] | Maximum [Member]
Site Contingency [Line Items]
Percentage of clean-up costs		50.00%
Yakama Nation [Member] | Portland Harbor Other [Member]
Site Contingency [Line Items]
Trustee Council Members - Number of Claimants				1
Site Contingency, Number of Other Third-Party Defendants					29
NRD liability claim yakama nation					$ 300
Number of Amended Complaints Filed				2

Environmental Matters - Regulat

Environmental Matters - Regulatory Deferred Assets (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Site Contingency [Line Items]
Regulatory Assets, Current	$ 46,317	$ 41,930	$ 45,900
Regulatory Assets, Noncurrent	$ 327,194	$ 371,786	$ 343,037
Remediation Non-recovery Percentage	3.32%	3.32%	3.32%
Annual tariff rider collection	$ 5,000
Annual insurance proceeds to apply against remediation costs	5,000
Total annual remediation expense and interest	10,000
Environmental Earnings Test Reserve	$ 4,400
Oregon [Member]
Site Contingency [Line Items]
Remediation Recovery Percentage	96.68%	96.68%	96.68%
Front Street [Member] | Environmental costs [Member]
Site Contingency [Line Items]
Accrued site liabilities	$ 400	$ 400	$ 400
Northwest Natural Gas Company [Member]
Site Contingency [Line Items]
Regulatory Assets, Current	46,317	41,930	45,900
Regulatory Assets, Noncurrent	327,194	371,786	343,037
Northwest Natural Gas Company [Member] | Environmental costs [Member]
Site Contingency [Line Items]
Deferred costs and interest	36,874	41,883	44,686
Accrued site liabilities	124,133	128,369	122,962
Insurance proceeds and interest	(89,305)	(88,502)	(95,100)
Regulatory Assets	71,702	81,750	72,548
Regulatory Assets, Current	5,090	5,601	5,818
Regulatory Assets, Noncurrent	$ 66,612	$ 76,149	$ 66,730

Discontinued Operations (Detail

Discontinued Operations (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Disposal Group, Including Discontinued Operation, Classified Balance Sheet Disclosures [Abstract]
Discontinued operations - current assets	$ 14,632	$ 1,512		$ 13,269
Discontinued operations - non-current assets	0	10,859		0
Discontinued operations - total assets		12,400
Discontinued operations current liabilities	13,282	1,209		12,959
Discontinued operations non-current liabilities	0	11,979		0
Discontinued Operation, Income Statement Disclosures [Abstract]
Loss from discontinued operations, net of tax	(217)	(474)
Gill Ranch [Member] | Discontinued Operations, Held-for-sale or Disposed of by Sale [Member]
Disposal Group, Including Discontinued Operation, Classified Balance Sheet Disclosures [Abstract]
Accounts receivable	1,277	193		390
Inventories	627	736		685
Other current assets	337	583		333
Property, plant, and equipment	12,033	10,812		11,621
Less: Accumulated depreciation	7	4		7
Operating lease right of use asset	118	0		0
Other non-current assets	247	51		247
Discontinued operations - current assets	14,632	1,512		13,269
Discontinued operations - non-current assets	0	10,859		0
Discontinued operations - total assets	14,632	12,371		13,269
Accounts payable	1,102	462		873
Taxes accrued	59	334		0
Other current liabilities	300	413		307
Operating lease liabilities	111	0		0
Other non-current liabilities	11,710	11,979		11,779
Discontinued operations current liabilities	13,282	1,209		12,959
Discontinued operations non-current liabilities	0	11,979		0
Total discontinued operations liabilities	13,282	13,188		$ 12,959
Gill Ranch [Member] | Discontinued Operations, Held-for-sale [Member]
Discontinued Operation, Income Statement Disclosures [Abstract]
Revenues	1,721	1,077
Operations and maintenance	1,613	1,036
General taxes	59	334
Depreciation and amortization	106	110
Other expenses and interest	237	241
Total expenses	2,015	1,721
Loss from discontinued operations before income tax	(294)	(644)
Income tax benefit	(77)	(170)
Loss from discontinued operations, net of tax	$ (217)	$ (474)
Loss from discontinued operations per share of common stock
Basic (in dollars per share)	$ (0.01)	$ (0.02)
Diluted (in dollars per share)	$ (0.01)	$ (0.02)
Transferred Subsidiaries - NW Natural Discontinued Operations [Member] | Discontinued Operations, Disposed of by Means Other than Sale [Member]
Disposal Group, Including Discontinued Operation, Classified Balance Sheet Disclosures [Abstract]
Cash		$ 311
Accounts receivable		193
Receivables from affiliates		3,852
Inventories		736
Other current assets		639
Property, plant, and equipment		11,186
Less: Accumulated depreciation		203
Other investments		13,691
Other non-current assets		64
Discontinued operations - current assets		5,731
Discontinued operations - non-current assets		24,738
Discontinued operations - total assets		30,469
Accounts payable		731
Taxes accrued		368
Payables to affiliates		660
Other current liabilities		401
Deferred tax liabilities		(16,397)
Other non-current liabilities		12,067
Discontinued operations current liabilities		2,160
Discontinued operations non-current liabilities		(4,330)
Total discontinued operations liabilities		2,170
Discontinued Operation, Income Statement Disclosures [Abstract]
Revenues		1,133
Operations and maintenance		1,059
General taxes		347
Depreciation and amortization		117
Other expenses and interest		260
Total expenses		1,783
Loss from discontinued operations before income tax		(650)
Income tax benefit		(173)
Loss from discontinued operations, net of tax		$ (477)
Gill Ranch [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Percent ownership	75.00%
Pacific Gas and Electric Company [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Percent ownership	25.00%
Scenario, Forecast [Member] | Minimum [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from divestiture of businesses			$ 25,000
Scenario, Forecast [Member] | Maximum [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from divestiture of businesses			$ 26,500