Northwest Natural Holding (NWN) 10-Q 8 May 20 2020 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2020	Apr. 28, 2020
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Mar. 31, 2020
Entity File Number	1-38681
Entity Registrant Name	NORTHWEST NATURAL HOLDING COMPANY
Entity Incorporation, State or Country Code	OR
Entity Tax Identification Number	82-4710680
Entity Address, Address Line One	250 SW Taylor Street
Entity Address, City or Town	Portland
Entity Address, State or Province	OR
Entity Address, Postal Zip Code	97204
City Area Code	(503)
Local Phone Number	226-4211
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Title of 12(b) Security	Common Stock
Trading Symbol	NWN
Security Exchange Name	NYSE
Entity Common Stock, Shares Outstanding		30,528,958
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Central Index Key	0001733998
Northwest Natural Gas Company [Member]
Document Information [Line Items]
Document Type	10-Q
Document Period End Date	Mar. 31, 2020
Entity File Number	1-15973
Entity Registrant Name	NORTHWEST NATURAL GAS COMPANY
Entity Incorporation, State or Country Code	OR
Entity Tax Identification Number	93-0256722
Entity Address, Address Line One	250 SW Taylor Street
Entity Address, City or Town	Portland
Entity Address, State or Province	OR
Entity Address, Postal Zip Code	97204
City Area Code	(503)
Local Phone Number	226-4211
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Central Index Key	0000073020

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Operating revenues [Abstract]
Operating revenues	$ 285,151	$ 285,348
Operating expenses:
Cost of gas	108,538	105,457
Operations and maintenance	48,921	51,482
Environmental remediation	4,005	8,947
General taxes	9,895	9,027
Excise Taxes	11,743	11,926
Depreciation and amortization	24,675	21,572
Other operating expenses	928	892
Total operating expenses	208,705	209,303
Income from operations	76,446	76,045
Other income (expense), net	(3,575)	(13,747)
Interest expense, net	10,468	10,205
Income before income taxes	62,403	52,093
Income tax expense	14,127	8,675
Net income from continuing operations	48,276	43,418
Loss from discontinued operations, net of tax	(778)	(217)
Net income	47,498	43,201
Other comprehensive income:
Amortization of non-qualified employee benefit plan liability, net of taxes	160	115
Comprehensive income	$ 47,658	$ 43,316
Average common shares outstanding:
Basic (in shares)	30,491	28,906
Diluted (in shares)	30,535	28,970
Earnings from continuing operations per share of common stock:
Basic (in dollars per share)	$ 1.58	$ 1.50
Diluted (in dollars per share)	1.58	1.50
Loss from discontinued operations per share of common stock:
Basic (in dollars per share)	(0.02)	(0.01)
Diluted (in dollars per share)	(0.02)	(0.01)
Earnings (loss) per share of common stock:
Basic (in dollars per share)	1.56	1.49
Diluted (in dollars per share)	$ 1.56	$ 1.49
Northwest Natural Gas Company [Member]
Operating revenues [Abstract]
Operating revenues	$ 282,529	$ 284,846
Operating expenses:
Cost of gas	108,595	105,513
Operations and maintenance	46,256	50,434
Environmental remediation	4,005	8,947
General taxes	9,799	8,988
Excise Taxes	11,743	11,926
Depreciation and amortization	24,190	21,504
Other operating expenses	920	890
Total operating expenses	205,508	208,202
Income from operations	77,021	76,644
Other income (expense), net	(3,563)	(13,768)
Interest expense, net	9,861	10,133
Income before income taxes	63,597	52,743
Income tax expense	14,418	8,848
Net income	49,179	43,895
Other comprehensive income:
Amortization of non-qualified employee benefit plan liability, net of taxes	160	115
Comprehensive income	$ 49,339	$ 44,010

Consolidated Statements of Co_2

Consolidated Statements of Comprehensive Income (Parentheticals) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Amortization of non-qualified employee benefit plan liability, tax	$ 58	$ 41
Northwest Natural Gas Company [Member]
Amortization of non-qualified employee benefit plan liability, tax	$ 58	$ 41

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Current assets:
Cash and cash equivalents	$ 471,079	$ 9,648	$ 12,817
Accounts receivable	78,083	67,137	93,617
Accrued unbilled revenue	41,871	56,192	36,147
Allowance for uncollectible accounts	(1,335)	(673)	(1,301)
Regulatory assets	37,815	41,929	46,317
Derivative instruments	2,257	6,802	7,890
Inventories	34,390	43,985	19,540
Gas reserves	14,351	15,278	16,157
Income Taxes Receivable, Current	0	256	6,000
Other current assets	26,460	38,004	20,293
Discontinued operations current assets	15,296	15,134	14,632
Total current assets	720,267	293,692	272,109
Non-current assets:
Property, plant, and equipment	3,551,065	3,476,746	3,439,460
Less: Accumulated depreciation	1,050,850	1,037,847	1,005,117
Property, Plant and Equipment, Net	2,500,215	2,438,899	2,434,343
Gas reserves	45,234	48,394	61,907
Regulatory assets	328,024	343,146	327,194
Derivative instruments	2,451	3,337	541
Other investments	61,928	63,333	63,829
Operating lease right of use asset	79,522	2,950	6,163
Assets under sales-type leases	146,937	146,310	990
Goodwill	69,220	49,929	8,954
Other non-current assets	47,729	38,464	15,087
Total non-current assets	3,281,260	3,134,762	2,919,008
Total assets	4,001,527	3,428,454	3,191,117
Current liabilities:
Short-term debt	550,000	149,100	176,391
Current maturities of long-term debt	202	75,109	104,158
Accounts payable	86,766	113,370	103,207
Taxes accrued	23,837	11,971	11,004
Interest accrued	9,396	7,451	9,233
Regulatory liabilities	47,137	44,657	46,770
Derivative instruments	5,036	2,000	2,845
Operating lease liabilities	1,071	2,101	4,656
Other current liabilities	62,624	62,705	54,543
Discontinued operations current liabilities	12,801	13,709	13,282
Total current liabilities	798,870	482,173	526,089
Long-term debt	953,962	805,955	632,484
Deferred credits and other non-current liabilities:
Deferred tax liabilities	300,168	295,643	293,662
Regulatory liabilities	623,219	625,717	600,698
Pension and other postretirement benefit liabilities	224,490	228,129	220,732
Derivative instruments	939	609	1,161
Operating lease liabilities	79,105	841	1,495
Other non-current liabilities	119,033	123,388	120,569
Total deferred credits and other non-current liabilities	1,346,954	1,274,327	1,238,317
Commitments and contingencies (see Note 16 and Note 17)
Equity:
Common stock	561,264	558,282	459,932
Retained earnings	351,050	318,450	342,734
Accumulated other comprehensive loss	(10,573)	(10,733)	(8,439)
Total equity	901,741	865,999	794,227
Total liabilities and equity	4,001,527	3,428,454	3,191,117
Northwest Natural Gas Company [Member]
Current assets:
Cash and cash equivalents	432,255	5,919	6,833
Accounts receivable	77,340	66,823	93,502
Accrued unbilled revenue	41,809	56,139	36,085
Receivables from affiliates	2,718	787	4,247
Allowance for uncollectible accounts	(1,334)	(672)	(1,300)
Regulatory assets	37,815	41,929	46,317
Derivative instruments	2,257	6,802	7,890
Inventories	34,279	43,896	19,528
Gas reserves	14,351	15,278	16,157
Other current assets	26,290	33,258	19,474
Total current assets	667,780	270,159	248,733
Non-current assets:
Property, plant, and equipment	3,509,049	3,456,075	3,435,304
Less: Accumulated depreciation	1,049,135	1,036,593	1,004,812
Property, Plant and Equipment, Net	2,459,914	2,419,482	2,430,492
Gas reserves	45,234	48,394	61,907
Regulatory assets	328,024	343,146	327,194
Derivative instruments	2,451	3,337	541
Other investments	48,450	49,837	50,212
Operating lease right of use asset	79,383	2,760	5,903
Assets under sales-type leases	146,937	146,310	990
Other non-current assets	47,223	38,062	14,656
Total non-current assets	3,157,616	3,051,328	2,891,895
Total assets	3,825,396	3,321,487	3,140,628
Current liabilities:
Short-term debt	450,000	125,100	176,300
Current maturities of long-term debt	0	74,907	104,084
Accounts payable	85,604	111,641	102,232
Payables to affiliates	21,353	1,546	1,385
Taxes accrued	11,621	11,717	10,869
Interest accrued	9,368	7,441	9,225
Regulatory liabilities	47,137	44,657	46,770
Derivative instruments	5,036	2,000	2,845
Operating lease liabilities	984	1,979	4,477
Other current liabilities	61,218	61,438	53,155
Total current liabilities	692,321	442,426	511,342
Long-term debt	917,146	769,081	630,370
Deferred credits and other non-current liabilities:
Deferred tax liabilities	312,436	309,297	307,704
Regulatory liabilities	622,375	625,717	600,698
Pension and other postretirement benefit liabilities	224,490	228,129	220,732
Derivative instruments	939	609	1,161
Operating lease liabilities	79,052	772	1,413
Other non-current liabilities	118,898	123,260	120,465
Total deferred credits and other non-current liabilities	1,358,190	1,287,784	1,252,173
Equity:
Common stock	319,557	319,557	226,452
Retained earnings	548,755	513,372	528,730
Accumulated other comprehensive loss	(10,573)	(10,733)	(8,439)
Total equity	857,739	822,196	746,743
Total liabilities and equity	$ 3,825,396	$ 3,321,487	$ 3,140,628

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parentheticals) - $ / shares shares in Thousands, $ / shares in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Statement of Financial Position [Abstract]
Shares outstanding (in shares)	30,528	30,472	28,962
Shares Authorized (in shares)	100,000	100,000	100,000
Shares issued (in shares)	30,528	30,472	28,962
Par Value (in dollars per share)	$ 0	$ 0	$ 0

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, 2018	$ 762,634	$ 457,640	$ 312,182	$ (7,188)	$ 715,668		$ 496,404	$ (7,188)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	43,201		43,201		43,895		43,895
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]			1,366	(1,366)			1,366	(1,366)
Other comprehensive income	43,316			115	44,010			115
Stock-based compensation		1,245
Shares issued pursuant to equity based plans		1,047
Adjustments to Additional Paid in Capital, Stock Issued, Issuance Costs		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
Beginning Balance at Dec. 31, 2019	$ 865,999	558,282	318,450	(10,733)	822,196		513,372	(10,733)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	47,498		47,498		49,179		49,179
Dividends on common stock			(14,898)				(13,796)
Stranded Deferred Tax Remeasurement Benefit	0
Stranded Deferred Tax Remeasurement Benefit | Accounting Standards Update 2018-02 [Member]			0	0			0	0
Other comprehensive income	47,658			160	49,339			160
Stock-based compensation		3,378
Shares issued pursuant to equity based plans		(390)
Adjustments to Additional Paid in Capital, Stock Issued, Issuance Costs		(6)
Ending Balance at Mar. 31, 2020	$ 901,741	$ 561,264	$ 351,050	$ (10,573)	$ 857,739	$ 319,557	$ 548,755	$ (10,573)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends per share of common stock	$ 0.4775

Consolidated Statement of Cash

Consolidated Statement of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Operating activities:
Net income	$ 47,498	$ 43,201
Adjustments to reconcile net income to cash provided by operations:
Depreciation, Depletion and Amortization	24,675	21,572
Regulatory amortization of gas reserves	4,087	4,780
Deferred income taxes	(3,422)	6,306
Qualified defined benefit pension plan expense	4,446	3,499
Contributions to qualified defined benefit pension plans	(3,160)	(1,490)
Deferred environmental expenditures, net	(3,981)	(3,685)
Amortization of environmental remediation	4,005	8,947
Regulatory revenue recovery deferral from the TCJA	0	450
Regulatory disallowance of pension costs	0	10,500
Other	6,499	3,171
Changes in assets and liabilities:
Receivables, net	4,845	(4,891)
Inventories	9,571	21,108
Income and other taxes	21,911	7,406
Accounts payable	(23,430)	(14,883)
Interest accrued	1,945	1,927
Deferred gas costs	8,239	(19,182)
Decoupling mechanism	6,137	7,903
Other, net	(6,626)	8,894
Discontinued operations	(376)	(739)
Cash provided by operating activities	102,863	104,794
Investing activities:
Capital expenditures	(57,446)	(48,764)
Acquisitions, net of cash acquired	(37,883)	0
Leasehold improvement expenditures	(6,325)	(940)
Other	919	(1,051)
Discontinued operations	(694)	(301)
Cash used in investing activities	(101,429)	(51,056)
Financing activities:
Proceeds from stock options exercised	68	1,546
Long-term debt issued	150,000	0
Long-term debt retired	(75,000)	0
Proceeds from Short-term Debt	150,000	0
Change in short-term debt	250,900	(41,229)
Cash dividend payments on common stock	(13,834)	(12,935)
Other	(2,137)	(936)
Net Cash Provided by (Used in) Financing Activities	459,997	(53,554)
Increase in cash and cash equivalents	461,431	184
Cash and cash equivalents, beginning of period	9,648
Cash and cash equivalents, end of period	471,079	12,817
Supplemental disclosure of cash flow information:
Interest paid, net of capitalization	8,368	7,976
Income taxes paid (refunded), net	(256)	(90)
Northwest Natural Gas Company [Member]
Operating activities:
Net income	49,179	43,895
Adjustments to reconcile net income to cash provided by operations:
Depreciation, Depletion and Amortization	24,190	21,504
Regulatory amortization of gas reserves	4,087	4,780
Deferred income taxes	(3,897)	6,072
Qualified defined benefit pension plan expense	4,446	3,499
Contributions to qualified defined benefit pension plans	(3,160)	(1,490)
Deferred environmental expenditures, net	(3,981)	(3,685)
Amortization of environmental remediation	4,005	8,947
Regulatory revenue recovery deferral from the TCJA	0	450
Regulatory disallowance of pension costs	0	10,500
Other	6,061	3,117
Changes in assets and liabilities:
Receivables, net	2,798	(4,995)
Inventories	9,593	21,097
Income and other taxes	21,748	5,037
Accounts payable	(22,717)	(15,337)
Interest accrued	1,927	1,952
Deferred gas costs	8,239	(19,182)
Decoupling mechanism	6,137	7,903
Other, net	(4,593)	10,639
Cash provided by operating activities	104,062	104,703
Investing activities:
Capital expenditures	(56,234)	(48,658)
Leasehold improvement expenditures	(6,325)	(940)
Other	919	(1,051)
Cash used in investing activities	(61,640)	(50,649)
Financing activities:
Long-term debt issued	150,000	0
Long-term debt retired	(75,000)	0
Proceeds from Short-term Debt	150,000	0
Change in short-term debt	174,900	(41,200)
Cash dividend payments on common stock	(13,796)	(12,935)
Other	(2,190)	(1,033)
Net Cash Provided by (Used in) Financing Activities	383,914	(55,168)
Increase in cash and cash equivalents	426,336	(1,114)
Cash and cash equivalents, beginning of period	5,919
Cash and cash equivalents, end of period	432,255	6,833
Supplemental disclosure of cash flow information:
Interest paid, net of capitalization	7,795	7,889
Income taxes paid (refunded), net	$ 950	$ (90)

Organization and Principles of

Organization and Principles of Consolidation	3 Months Ended
	Mar. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Principles of Consolidation	ORGANIZATION AND PRINCIPLES OF CONSOLIDATION 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). 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; • Sunstone Infrastructure, LLC; • Sunriver Water, LLC (Sunriver Water); • Sunriver Environmental, LLC (Sunriver Environmental); ▪ NW Natural Water of Washington, LLC (NWN Water of Washington); • Cascadia Infrastructure, LLC; • Cascadia Water, LLC (Cascadia); • Suncadia Water Company, LLC (Suncadia Water); • Suncadia Environmental Company, LLC (Suncadia Environmental); ▪ NW Natural Water of Idaho, LLC (NWN Water of Idaho); • Gem State Water Company, LLC (Gem State); • Gem State Infrastructure, LLC; and ▪ NW Natural Water of Texas, LLC (NWN Water of Texas); • Blue Topaz Water, LLC; • Blue Topaz Infrastructure, LLC; and • T&W Water Service Company. 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 2019 Annual Report on Form 10-K ( 2019 Form 10-K). A significant part of NW Holdings' and 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. Seasonality affects the comparability of the results of other operations across quarters but not across years. 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 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.

Significant Accounting Policies

Significant Accounting Policies	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
Significant Accounting Policies	SIGNIFICANT ACCOUNTING POLICIES Significant accounting policies are described in Note 2 of the 2019 Form 10-K. There were no material changes to those accounting policies during the three months ended March 31, 2020 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), Idaho Public Utilities Commission (IPUC) or Public Utility Commission of Texas (PUCT), 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 for NW Holdings and NW Natural were as follows: Regulatory Assets March 31, December 31, In thousands 2020 2019 2019 NW Natural: Current: Unrealized loss on derivatives (1) $ 4,845 $ 2,845 $ 2,000 Gas costs 10,898 17,927 20,140 Environmental costs (2) 4,459 5,090 4,762 Decoupling (3) 610 3,937 1,969 Pension balancing (4) 6,794 4,955 5,939 Income taxes 3,576 2,209 2,209 Other (5) 6,633 9,354 4,910 Total current $ 37,815 $ 46,317 $ 41,929 Non-current: Unrealized loss on derivatives (1) $ 939 $ 1,161 $ 609 Pension balancing (4) 46,031 50,408 48,251 Income taxes 16,354 17,758 17,173 Pension and other postretirement benefit liabilities 168,676 171,565 173,262 Environmental costs (2) 82,491 66,612 87,624 Gas costs 350 8,919 2,866 Decoupling (3) — 250 — Other (5) 13,183 10,521 13,361 Total non-current $ 328,024 $ 327,194 $ 343,146 Regulatory Liabilities March 31, December 31, In thousands 2020 2019 2019 NW Natural: Current: Gas costs $ 4,046 $ 11,126 $ 1,223 Unrealized gain on derivatives (1) 2,257 7,284 6,622 Decoupling (3) 11,203 2,055 4,831 Income taxes 7,522 7,763 8,435 Other (5) 22,109 18,542 23,546 Total current $ 47,137 $ 46,770 $ 44,657 Non-current: Gas costs $ 1,328 $ 1,421 $ 2,013 Unrealized gain on derivatives (1) 2,451 541 3,337 Decoupling (3) 4,784 614 6,378 Income taxes (6) 192,644 202,692 198,219 Accrued asset removal costs (7) 408,212 384,702 401,893 Other (5) 12,956 10,728 13,877 Total non-current - NW Natural $ 622,375 $ 600,698 $ 625,717 Other (NW Holdings) 844 — — Total non-current - NW Holdings $ 623,219 $ 600,698 $ 625,717 (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, 2020 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 Holdings and NW Natural would be required to write-off the net unrecoverable balances in the period such determination is made. We have applied for regulatory deferrals in the states in which we operate to recover the novel coronavirus (COVID-19) related costs such as incremental bad debt expense, forgone revenues related to late fees and reconnection fees, and other costs that may arise related to the COVID-19 pandemic. As of March 31, 2020 , we identified $0.7 million in incremental costs and lost revenue, of which approximately $0.4 million is related to increased bad debt expense. However, until the deferral is probable of recovery, any incremental expenses will be recognized in the results of operations. 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 Holdings' or NW Natural's consolidated financial position or results of operations. Recently Adopted Accounting Pronouncements 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 requires 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 were effective beginning January 1, 2020 and were applied with modified retrospective methodology. The adoption of this ASU did not materially affect the financial statements and disclosures of NW Holdings or NW Natural. The majority of NW Holdings' and NW Natural's financial assets are either short-term in nature, such as trade receivables, or relate to leased gas facilities under approved rate schedules. Allowance for trade receivables. Accounts receivable consist primarily of amounts due for natural gas sales and transportation services to NGD customers and amounts due for gas storage services. The payment term of these receivables is generally 15 days. NW Holdings and NW Natural establish allowances for uncollectible accounts (allowance) for trade receivables, including accrued unbilled revenue, based on customer types that share similar risk characteristics: residential, commercial, and industrial. For these short-term receivables, it is not expected that forecasted economic conditions would significantly affect the loss estimates under stable economic conditions. For extreme situations like a financial crisis, natural disaster, and the economic slowdown caused by pandemics like COVID-19, we enhance our review and analysis. Please refer to the section on COVID-19 impact below for more discussion. COVID-19 Impact. COVID-19, which was declared a pandemic by the World Health Organization in March 2020, has resulted in widespread global, national and local effects. On March 23, 2020, the Governors of Oregon and Washington, the states in which NW Natural’s service territories are located, issued stay at home executive orders. These and subsequent executive orders required the closure of “non-essential” businesses and permitted the continuation of “essential services.” As a result of these measures, NW Natural issued a notification in mid-March that it would not charge late payment fees or disconnect customers for late payment. Furthermore, we suspended sending outstanding receivable balances to collections. After taking into the consideration the significant exposure to quarantine-related job losses in Oregon and Washington state, NW Holdings and NW Natural looked beyond our standard review procedures for our allowance for uncollectible accounts calculation, including analyzing the significant indications of unemployment rate and comparing to historic economic data during the 2007-2009 time period where the country experienced an economic recession. We then considered other qualitative information including data from our call center such as recent trends in credit-related calls. We also reviewed statistics from our website for increases in credit-related inquiries. Finally, we considered the economic stimulus provided by the federal government which could have a beneficial impact on residential and commercial customers' abilities to ultimately make payment on their accounts. Taking all of these factors into consideration, we concluded a reasonable adjustment to the uncollectible provision for customer accounts as of March 31, 2020 would be a 50% increase in net write-offs as a percentage of gas sales for residential and small commercial customers. Our method for estimating our industrial provision for uncollectible accounts remains the same as the level of accounts receivable was lower due to reduced demand in the first quarter of 2020. The following table presents the activity related to the NW Holdings provision for uncollectible accounts by pool, substantially all of which is related to NW Natural's accounts receivable: As of As of January 1, 2020 Three Months Ended March 31, 2020 March 31, 2020 In thousands Beginning Balance Provision recorded Write-offs recognized Write-offs recovered Ending Balance Allowance for uncollectible accounts related to accounts receivable: Residential $ 432 $ 445 $ 6 $ — $ 883 Commercial 57 220 — (34 ) 243 Industrial 72 27 — (1 ) 98 Accrued unbilled and other 112 2 — (3 ) 111 Total $ 673 $ 694 $ 6 $ (38 ) $ 1,335 Allowance for net investments in sales-type leases. NW Natural currently holds two net investments in sales-type leases, with substantially all of the net investment balance related to the North Mist natural gas storage agreement with Portland General Electric (PGE) which is billed under an OPUC-approved rate schedule. See Note 6 for more information on the North Mist lease. Due to the nature of this service, PGE may recover the costs of the lease through general rate cases. Therefore, we expect the risk of loss due to the credit of this lessee to be very low. As such, no allowance for uncollectibility was recorded for our sales-type lease receivables. NW Natural will continue monitoring the credit health of the lessees and the overall economic environment, including the economic factors closely tied to the financial health of our current and future lessees. 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 were effective for us beginning January 1, 2020. 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. NW Holdings and NW Natural do not have either Level 3 fair value measurements or transfers between Level 1 or Level 2 in their current portfolios. The adoption did not have an impact on the financial statements or disclosures of NW Holdings or NW Natural. 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 were effective for us beginning January 1, 2020 and were applied retrospectively. The adoption of this ASU did not materially affect the financial statements and disclosures of NW Holdings or NW Natural. 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. 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. Recently Issued Accounting Pronouncements INCOME TAXES. On December 18, 2019, the FASB issued ASU 2019-12, "Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes." The purpose of the amendment is to reduce cost and complexity related to accounting for income taxes by removing certain exceptions to the general principles and improving consistent application for other areas in Topic 740. The amendments in this update are effective for us beginning January 1, 2021. Early adoption is permitted. The amended presentation and disclosure guidance should be applied retrospectively. We do not expect this ASU to materially affect the financial statements and disclosures of NW Holdings or NW Natural. REFERENCE RATE REFORM. On March 12, 2020, the FASB issued ASU 2020-04, "Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting." The purpose of the amendment is to provide optional expedients and exceptions for applying generally accepted accounting principles (GAAP) to contracts, hedging relationships, and other transactions affected by reference rate reform if certain criteria are met. The amendments in this Update apply only to contracts, hedging relationships, and other transactions that reference LIBOR or another reference rate expected to be discontinued because of reference rate reform. The amendments in this Update are effective for all entities as of March 12, 2020 through December 31, 2022. We do not expect this ASU to materially affect the financial statements and disclosures of NW Holdings or NW Natural.

Earnings Per Share

Earnings Per Share	3 Months Ended
	Mar. 31, 2020
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. Anti-dilutive 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 2020 2019 Net income from continuing operations $ 48,276 $ 43,418 Loss from discontinued operations, net of tax (778 ) (217 ) Net income $ 47,498 $ 43,201 Average common shares outstanding - basic 30,491 28,906 Additional shares for stock-based compensation plans (See Note 7) 44 64 Average common shares outstanding - diluted 30,535 28,970 Earnings from continuing operations per share of common stock: Basic $ 1.58 $ 1.50 Diluted $ 1.58 $ 1.50 Loss from discontinued operations per share of common stock: Basic $ (0.02 ) $ (0.01 ) Diluted $ (0.02 ) $ (0.01 ) Earnings per share of common stock: Basic $ 1.56 $ 1.49 Diluted $ 1.56 $ 1.49 Additional information: Anti-dilutive shares 3 5

Segment Information

Segment Information	3 Months Ended
	Mar. 31, 2020
Segment Reporting [Abstract]
Segment Information	We primarily operat e in one reportable business segment, which is NW Natural's local gas distribution business and is referred to as the NGD s egment. 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, 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, 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 prospective NGD customer billing credits. NW Holdings NW Holdings' activities in Other include all remaining activities not associated with NW Natural, specifically: NWN Water, which consolidates the water and wastewater utility operations and is pursuing other investments in the water sector through itself and 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, including certain business development activities . Segment Information Summary Inter-segment transactions were immaterial for the periods presented. The following table presents summary financial information concerning the reportable segment and other 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 2020 Operating revenues $ 278,487 $ 4,042 $ 282,529 $ 2,622 $ 285,151 Depreciation and amortization 23,946 244 24,190 485 24,675 Income (loss) from operations 75,258 1,763 77,021 (575 ) 76,446 Net income (loss) from continuing operations 47,943 1,236 49,179 (903 ) 48,276 Capital expenditures 56,157 77 56,234 1,212 57,446 Total assets at March 31, 2020 (1) 3,776,650 48,746 3,825,396 160,835 3,986,231 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 Total assets at December 31, 2019 (1) 3,273,835 47,652 3,321,487 91,833 3,413,320 (1) Total assets for NW Holdings exclude assets related to discontinued operations of $15.3 million , $14.6 million , and $15.1 million as of March 31, 2020 , March 31, 2019 , and December 31, 2019 , respectively. 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 when applicable. This is offset by environmental remediation expense presented 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 2020 2019 NGD margin calculation: NGD distribution revenues $ 273,561 $ 278,983 Other regulated services 4,926 58 Total NGD operating revenues 278,487 279,041 Less: NGD cost of gas 108,595 105,513 Environmental remediation 4,005 8,947 Revenue taxes 11,743 11,926 NGD margin $ 154,144 $ 152,655

Revenue (Notes)

Revenue (Notes)	3 Months Ended
	Mar. 31, 2020
Revenue from Contract with Customer [Abstract]
Revenue from Contract with Customer	REVENUE The following tables present disaggregated revenue from continuing operations: Three Months Ended March 31, In thousands NGD Other (NW Natural) NW Natural Other (NW Holdings) NW Holdings 2020 Natural gas sales $ 274,004 $ — $ 274,004 $ — $ 274,004 Gas storage revenue, net — 2,336 2,336 — 2,336 Asset management revenue, net — 150 150 — 150 Appliance retail center revenue — 1,556 1,556 — 1,556 Other revenue 337 — 337 2,622 2,959 Revenue from contracts with customers 274,341 4,042 278,383 2,622 281,005 Alternative revenue (472 ) — (472 ) — (472 ) Leasing revenue 4,618 — 4,618 — 4,618 Total operating revenues $ 278,487 $ 4,042 $ 282,529 $ 2,622 $ 285,151 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 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. We evaluated the probability of collection in accordance with the current expected credit losses standard. 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 taxes are included in operating revenues with an equal and offsetting expense recognized in operating expense in the consolidated statements of comprehensive income. Revenue-based taxes are primarily franchise taxes, which are collected from NGD customers and remitted to taxing authorities. 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, 2020 . 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 revenues from NW Natural's North Mist Storage contract with Portland General Electric (PGE) in support of PGE'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. The facility is accounted for as a sales-type lease with regulatory accounting deferral treatment. The investment is included in rate base under an established cost-of-service tariff schedule, with revenues recognized according to the tariff schedule and as such, profit upon commencement was deferred and will be amortized over the lease term. Leasing revenue also contains rental revenue from small leases of property owned by NW Natural to third parties. The majority of these transactions are accounted for as operating leases and the revenue is recognized 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. Revenues include the optimization of the storage assets and pipeline capacity and are provided net of the profit sharing amount refunded to NGD customers. Certain asset management revenues received are 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. Additionally, other asset management revenues may be based on a fixed rate. Generally, asset management accounts are settled on a monthly basis. As of March 31, 2020 , unrecognized revenue for the fixed component of the transaction price related to gas storage and asset management revenue was approximately $69.7 million . Of this amount, approximately $12.3 million will be recognized during the remainder of 2020 , $18.2 million in 2021 , $14.5 million in 2022 , $11.6 million in 2023 , $7.8 million in 2024 and $5.3 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 and wastewater 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, Idaho and Texas 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, 2020 .

Leases (Notes)

Leases (Notes)	3 Months Ended
	Mar. 31, 2020
Leases [Abstract]
Leases of Lessee Disclosure	LEASES Lease Revenue Leasing revenue primarily consists of NW Natural's North Mist natural gas storage agreement with Portland General Electric (PGE) which is billed under an OPUC-approved rate schedule and includes an initial 30 -year term with options to extend, totaling up to an additional 50 years upon mutual agreement of the parties. Under U.S. GAAP, this agreement is classified as a sales-type lease and qualifies for regulatory accounting deferral treatment. The investment in the storage facility is included in rate base under a separately established cost-of-service tariff, with revenues recognized according to the tariff schedule. As such, the selling profit that was calculated upon commencement as part of the sale-type lease recognition was deferred and will be amortized over the lease term. Billing rates under the cost-of-service tariff will be updated annually to reflect current information including depreciable asset levels, forecasted operating expenses, and the results of regulatory proceedings, as applicable, and revenue received under this agreement is recognized as operating revenue on the consolidated statements of comprehensive income. There are no variable payments or residual value guarantees. The lease does not contain an option to purchase the underlying assets. NW Natural also maintains a sales-type lease for specialized compressor facilities to provide high pressure compressed natural gas (CNG) services. 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 selling profit computed upon lease commencement was not significant. Our lessor portfolio also contains small leases of property owned by NW Natural to third parties. These transactions are accounted for as operating leases and the revenue is recognized over the term of the lease agreement. The components of lease revenue at NW Natural were as follows: Three Months Ended March 31, In thousands 2020 2019 Lease revenue Operating leases $ 28 $ 48 Sales-type leases 4,590 60 Total lease revenue $ 4,618 $ 108 Total future minimum lease payments to be received under non-cancellable leases at NW Natural at March 31, 2020 are as follows: In thousands Operating Sales-Type Total Remainder of 2020 $ 56 $ 13,603 $ 13,659 2021 49 17,518 17,567 2022 45 17,026 17,071 2023 45 16,557 16,602 2024 45 15,867 15,912 Thereafter 94 266,563 266,657 Total lease revenue $ 334 $ 347,134 $ 347,468 Less: imputed interest 199,041 Total leases receivable $ 148,093 The total leases receivable above is reported under the NGD segment and the short- and long-term portions are included within other current assets and assets under sales-type leases on the consolidated balance sheets, respectively. The total amount of unguaranteed residual assets was $4.1 million and $4.0 million at March 31, 2020 and December 31, 2019 , respectively, and is included in assets under sales-type leases on the consolidated balance sheets. Additionally, under regulatory accounting, the revenues and expenses associated with these agreements are presented on the consolidated statements of comprehensive income such that their presentation aligns with similar regulated activities at NW Natural. Lease Expense Operating Leases We have operating leases for land, buildings and equipment. Our primary lease is for NW Natural's corporate operations center. Our leases have remaining lease terms of less than one year to 20 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 an estimated discount rate representing the rate we would have incurred to finance the funds necessary to purchase the leased asset and is 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, In thousands 2020 2019 NW Natural: Operating lease expense $ 1,202 1,142 Short-term lease expense 198 160 Other (NW Holdings): Operating lease expense $ 52 46 Short-term lease expense — — NW Holdings: Operating lease expense $ 1,254 1,188 Short-term lease expense 198 160 Supplemental balance sheet information related to operating leases as of March 31, 2020 is as follows: In thousands March 31, December 31, 2020 2019 2019 NW Natural: Operating lease right of use asset $ 79,383 $ 5,903 $ 2,760 Operating lease liabilities - current liabilities $ 984 $ 4,477 $ 1,979 Operating lease liabilities - non-current liabilities 79,052 1,413 772 Total operating lease liabilities $ 80,036 $ 5,890 $ 2,751 Other (NW Holdings): Operating lease right of use asset $ 139 $ 260 $ 190 Operating lease liabilities - current liabilities $ 87 $ 179 $ 122 Operating lease liabilities - non-current liabilities 53 82 69 Total operating lease liabilities $ 140 $ 261 $ 191 NW Holdings: Operating lease right of use asset $ 79,522 $ 6,163 $ 2,950 Operating lease liabilities - current liabilities $ 1,071 $ 4,656 $ 2,101 Operating lease liabilities - non-current liabilities 79,105 1,495 841 Total operating lease liabilities $ 80,176 $ 6,151 $ 2,942 The weighted-average remaining lease terms and weighted-average discount rates for the operating leases at NW Natural were as follows: In thousands March 31, December 31, 2020 2019 2019 Weighted-average remaining lease term (years) 19.7 1.3 1.0 Weighted-average discount rate 7.20 % 3.79 % 3.98 % Commencement of Significant Lease In October 2017, NW Natural entered into a 20 -year operating lease agreement for a new corporate operations center in Portland, Oregon in anticipation of the expiration of the current corporate operations center lease in 2020. The lease commenced in March 2020 upon substantial completion of the landlord's work. Total estimated base rent payments over the life of the lease are $159.3 million . There is an option to extend the term of the lease for two additional periods of seven years . There is a material timing difference between the minimum lease payments and expense recognition as calculated under operating lease accounting rules. OPUC issued an order allowing us to align our expense recognition with cash payments for ratemaking purposes. We recorded the difference between the minimum lease payments and the aggregate of the imputed interest on the finance lease obligation and amortization of the right-of-use asset as a deferred regulatory asset on our balance sheet. The balance of the regulatory asset as of March 31, 2020 was $0.6 million. Maturities of operating lease liabilities at March 31, 2020 were as follows: In thousands NW Natural Other NW Holdings Remainder of 2020 $ 3,117 $ 74 $ 3,191 2021 6,726 52 6,778 2022 6,848 18 6,866 2023 6,983 — 6,983 2024 7,146 — 7,146 Thereafter 130,935 — 130,935 Total lease payments 161,755 144 161,899 Less: imputed interest 81,719 4 81,723 Total lease obligations 80,036 140 80,176 Less: current obligations 984 87 1,071 Long-term lease obligations $ 79,052 $ 53 $ 79,105 As of March 31, 2020, finance lease liabilities with maturities of less than one year were $0.3 million at NW Natural. Cash Flow Information Supplemental cash flow information related to leases was as follows: Three Months Ended March 31, In thousands 2020 2019 NW Natural: Cash paid for amounts included in the measurement of lease liabilities Operating cash flows from operating leases $ 1,196 $ 1,091 Finance cash flows from finance leases 155 — Right of use assets obtained in exchange for lease obligations Operating leases $ 77,988 $ 6,987 Finance leases 233 — Other (NW Holdings): Cash paid for amounts included in the measurement of lease liabilities Operating cash flows from operating leases $ 52 $ 43 Right of use assets obtained in exchange for lease obligations Operating leases $ — $ 304 NW Holdings: Cash paid for amounts included in the measurement of lease liabilities Operating cash flows from operating leases $ 1,248 $ 1,134 Finance cash flows from finance leases 155 — Right of use assets obtained in exchange for lease obligations Operating leases $ 77,988 $ 7,291 Finance leases 233 — 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 $0.7 million , $0.2 million and $0.5 million at March 31, 2020

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2020
Share-based Payment Arrangement [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 8 in the 2019 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, 2020 , the final performance factor under the 2018 LTIP was approved and 39,784 performance-based shares were granted under the 2018 LTIP for accounting purposes. As such, NW Natural and other subsidiaries began recognizing compensation expense. In February 2020 and 2019, 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 2022 and 2021, respectively, there is not a mutual understanding of the awards' key terms and conditions between NW Holdings and the participants as of March 31, 2020 , and therefore, no expense was recognized for the 2020 and 2019 awards. NW Holdings will calculate the grant date fair value and NW Natural will recognize expense over the remaining service period for each award once the final performance factor has been approved. For the 2020 and 2019 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 2020 and 2019 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 performance period of three years for each respective award. If the targets were achieved for the 2020 and 2019 awards, NW Holdings would grant for accounting purposes 31,830 and 35,170 shares in the first quarters of 2022 and 2021, respectively. As of March 31, 2020 , there was $0.8 million of unrecognized compensation cost associated with the 2018 LTIP grants, which is expected to be recognized through 2020 . Restricted Stock Units During the three months ended March 31, 2020 , 31,076 RSUs were granted, under the LTIP with a weighted-average grant date fair value of $72.38 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. The majority of our RSU grants obligate NW Holdings, upon vesting, to issue the RSU holder one share of common stock. The grant may also include 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 depending on the structure of the award agreement. The fair value of an RSU is equal to the closing market price of common stock on the grant date. As of March 31, 2020 , there was $ 4.7 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 2025

Debt

Debt	3 Months Ended
	Mar. 31, 2020
Debt Disclosure [Abstract]
Debt	DEBT Short-Term Debt At March 31, 2020 , NW Holdings and NW Natural had short-term debt outstanding of $550.0 million and $450.0 million , respectively. NW Holdings' short-term debt consisted of $100.0 million in revolving credit agreement loan at NW Holdings, and at NW Natural $227.0 million in revolving credit agreement loans, a $150.0 million 364-day term loan, and $73.0 million of commercial paper. The carrying cost of commercial paper approximates fair value using Level 2 inputs. See Note 2 in the 2019 Form 10-K for a description of the fair value hierarchy. The maximum remaining maturity and average remaining maturity of NW Natural's commercial paper was 45 days and 25 days at March 31, 2020 . On March 23, 2020, NW Natural entered into a $150.0 million 364-day term loan credit agreement. NW Natural borrowed the full amount thereunder. The proceeds of which are expected to be used for general corporate purposes and to provide additional liquidity. All principal and unpaid interest under the Term Loan is due and payable on March 22, 2021. NW Natural may prepay the principal and interest, and amounts prepaid may not be reborrowed. The Term Loan requires that NW Natural maintain credit ratings with Standard & Poor’s and Moody’s Investor Services. A change in NW Natural’s debt ratings may result in a change to the interest rate on the Term Loan but is not an event of default. The Term Loan requires NW Natural to maintain a consolidated indebtedness to total capitalization ratio of 70% or less. Failure to comply with this covenant would entitle the banks to terminate their lending commitments and to accelerate the maturity of all amounts outstanding. NW Natural was in compliance with the covenant requiring the maintenance of an indebtedness to total capitalization ratio as of March 31, 2020 , with a consolidated indebtedness to total capitalization ratio of 61.4% . Long-Term Debt At March 31, 2020 , NW Holdings and NW Natural had long-term debt outstanding of $954.2 million and $917.1 million , respectively, which included $7.6 million of unamortized debt issuance costs at NW Natural. NW Natural's long-term debt consists of first mortgage bonds (FMBs) with maturity dates ranging from 2021 through 2050 , interest rates ranging from 2.822% to 9.050% , and a weighted average interest rate of 4.598% . In March 2020 , NW Natural issued $150.0 million of FMBs with an interest rate of 3.60% , due in 2050 . In February 2020, NW Natural retired $75.0 million of FMBs with an interest rate of 5.37% . In June 2019, NW Natural Water, a wholly-owned subsidiary of NW Holdings, entered into a new two-year term loan agreement for $35.0 million , due in 2021 . The loan carried an interest rate of 1.82% at March 31, 2020 , which is based upon the three-month LIBOR rate. The loan is guaranteed by NW Holdings and requires NW Holdings to maintain a consolidated indebtedness to total capitalization ratio of 70% or less . Failure to comply with this covenant would entitle the lenders to terminate their lending commitments and accelerate the maturity of all amounts outstanding. NW Holdings was in compliance with this covenant at March 31, 2020 , with a consolidated indebtedness to total capitalization ratio of 62.5% . 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 2019 Form 10-K for a description of the fair value hierarchy. The following table provides an estimate of the fair value of NW Holdings' long-term debt, including current maturities of long-term debt, using market prices in effect on the valuation date: NW Holdings March 31, December 31, In thousands 2020 2019 2019 Gross long-term debt $ 961,718 $ 741,888 $ 886,776 Unamortized debt issuance costs (7,554 ) (5,246 ) (5,712 ) Carrying amount $ 954,164 $ 736,642 $ 881,064 Estimated fair value (1) $ 1,038,691 $ 777,778 $ 957,268 (1) Estimated fair value does not include unamortized debt issuance costs. 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: NW Natural March 31, December 31, In thousands 2020 2019 2019 Gross long-term debt $ 924,700 $ 739,700 $ 849,700 Unamortized debt issuance costs (7,554 ) (5,246 ) (5,712 ) Carrying amount $ 917,146 $ 734,454 $ 843,988 Estimated fair value (1) $ 1,001,058 $ 775,590 $ 919,835 (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, 2020
Pension and Other Postretirement Benefits Cost (Reversal of Cost) [Abstract]
Pension and Other Postretirement Benefit Costs	PENSION AND OTHER POSTRETIREMENT BENEFIT COSTS NW Natural maintains a qualified non-contributory defined benefit pension plan (Pension Plan), non-qualified supplemental pension plans for eligible executive officers and other key employees, and other postretirement employee benefit plans. NW Natural also has a qualified defined contribution plan (Retirement K Savings Plan) for all eligible employees. The Pension Plan and Retirement K Savings Plan have plan assets, which are held in qualified trusts to fund retirement benefits. 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 2020 2019 2020 2019 Service cost $ 1,657 $ 1,517 $ 64 $ 68 Interest cost 4,011 4,662 223 281 Expected return on plan assets (5,496 ) (5,207 ) — — Amortization of prior service costs — 2 (117 ) (117 ) Amortization of net actuarial loss 4,778 3,603 143 97 Net periodic benefit cost 4,950 4,577 313 329 Amount allocated to construction (668 ) (586 ) (23 ) (24 ) Net periodic benefit cost charged to expense 4,282 3,991 290 305 Regulatory pension disallowance — 10,500 — — Amortization of regulatory balancing account 2,801 12,511 — — Net amount charged to expense $ 7,083 $ 27,002 $ 290 $ 305 Net periodic benefit costs are reduced by amounts capitalized to NGD plant. 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. The Order allowed for the application of certain deferred revenues and tax benefits from the TCJA to reduce 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 in the first quarter of 2019, 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. Amortization of the remaining amount of the balancing account began in the second quarter of 2019 in accordance with the Order. 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 2020 2019 Beginning balance $ (10,733 ) $ (7,188 ) Amounts reclassified from AOCL: Amortization of actuarial losses 218 156 Reclassification of stranded tax effects (1) — (1,366 ) Total reclassifications before tax 218 (1,210 ) Tax (benefit) expense (58 ) (41 ) Total reclassifications for the period 160 (1,251 ) Ending balance $ (10,573 ) $ (8,439 ) (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, 2020 , NW Natural made cash contributions totaling $3.2 million to qualified defined benefit pension plans. NW Natural expects further plan contributions of $25.0 million during the remainder of 2020 . 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 $2.5 million and $2.1 million for the three months ended March 31, 2020 and 2019 , respectively. See Note 10 in the 2019 Form 10-K for more information concerning these retirement and other postretirement benefit plans.

Income Tax

Income Tax	3 Months Ended
	Mar. 31, 2020
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 federal statutory rate due to the following: Three Months Ended March 31, NW Holdings NW Natural In thousands 2020 2019 2020 2019 Income tax at statutory rate (federal) $ 13,105 $ 11,022 $ 13,355 $ 11,159 State 3,677 3,291 3,737 3,326 Increase (decrease): Differences required to be flowed-through by regulatory commissions (2,525 ) (5,260 ) (2,525 ) (5,260 ) Other, net (130 ) (378 ) (149 ) (377 ) Total provision for income taxes on continuing operations $ 14,127 $ 8,675 $ 14,418 $ 8,848 Effective income tax rate for continuing operations 22.8 % 16.7 % 22.8 % 16.8 % The NW Holdings and NW Natural effective income tax rates for the three months ended March 31, 2020 compared to the same periods in 2019 changed primarily as a result of changes in pre-tax income and regulatory amortization of deferred TCJA benefits as approved in the March 2019 OPUC order. See " U.S. Federal TCJA Matters" below and Note 11 in the 2019 Form 10-K for more detail on income taxes and effective tax rates. The 2018 and 2019 tax years are currently under IRS examination as part of the Compliance Assurance Process (CAP). The 2020 tax year CAP application has been accepted by the IRS. 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 11 in the 2019 Form 10-K.

Property, Plant and Equipment (

Property, Plant and Equipment (Notes)	3 Months Ended
	Mar. 31, 2020
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 2020 2019 2019 NW Natural: NGD plant in service $ 3,344,345 $ 3,159,754 $ 3,302,049 NGD work in progress 95,566 204,938 84,965 Less: Accumulated depreciation 1,030,234 985,961 1,017,931 NGD plant, net 2,409,677 2,378,731 2,369,083 Other plant in service 64,314 65,283 63,513 Other construction work in progress 4,824 5,329 5,548 Less: Accumulated depreciation 18,901 18,851 18,662 Other plant, net 50,237 51,761 50,399 Total property, plant, and equipment $ 2,459,914 $ 2,430,492 $ 2,419,482 Other (NW Holdings): Other plant in service $ 42,016 $ 4,156 $ 20,671 Less: Accumulated depreciation 1,715 305 1,254 Other plant, net $ 40,301 $ 3,851 $ 19,417 NW Holdings: Total property, plant, and equipment $ 2,500,215 $ 2,434,343 $ 2,438,899 NW Natural and NW Holdings: Capital expenditures in accrued liabilities $ 33,999 $ 25,035 $ 32,502 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 May 2019, NW Natural placed its North Mist gas storage expansion project into service and commenced storage services to the facility's single customer, Portland General Electric (PGE). Under U.S. GAAP, this agreement is classified as a sales-type lease and qualifies for regulatory accounting deferral treatment. Accordingly, the project was de-recognized from property, plant and equipment upon lease commencement and the investment balance is presented net of the current portion of scheduled billings within assets under sales-type leases on the consolidated balance sheets. A total of $146.0 million was de-recognized from plant on the lease commencement date. See Note 6 for information regarding leases, including North Mist.

Gas Reserves

Gas Reserves	3 Months Ended
	Mar. 31, 2020
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, 2020 . 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 13 in the 2019 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 2020 2019 2019 Gas reserves, current $ 14,351 $ 16,157 $ 15,278 Gas reserves, non-current 172,956 171,150 172,029 Less: Accumulated amortization 127,722 109,243 123,635 Total gas reserves (1) 59,585 78,064 63,672 Less: Deferred taxes on gas reserves 14,522 19,638 15,515 Net investment in gas reserves $ 45,063 $ 58,426 $ 48,157 (1) The net investment in additional wells included in total gas reserves was $ 3.6 million , $ 4.5 million and $ 3.8 million at March 31, 2020 and 2019 and December 31, 2019 , 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, 2020
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 TC Energy 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, 2020 and 2019 and December 31, 2019 . See Note 14 in the 2019 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 14 in the 2019

Business Combinations Business

Business Combinations Business Combinations	3 Months Ended
	Mar. 31, 2020
Business Combinations [Abstract]
Business Combination Disclosure	BUSINESS COMBINATIONS 2020 Business Combinations During the three months ended March 31, 2020 , NWN Water and its subsidiaries completed two acquisitions qualifying as business combinations. The aggregate fair value of the preliminary cash consideration transferred for these acquisitions was $38.1 million , most of which was preliminarily allocated to property, plant and equipment and goodwill. These transactions align with NW Holdings' water sector strategy as it continues to expand its water services territories in the Pacific Northwest and beyond and included: • Suncadia Water Company , LLC and Suncadia Environmental Company, LLC were acquired by NWN Water of Washington on January 31, 2020, and • T&W Water Service Company was acquired by NWN Water of Texas on March 2, 2020. As each of these acquisitions met the criteria of a business combination, a preliminary allocation of the consideration to the acquired net assets based on their estimated fair value as of the acquisition date was performed. The allocation for each of these business combinations is considered preliminary as of March 31, 2020 , as facts and circumstances that existed as of the acquisition date may be discovered as we continue to integrate these businesses. In accordance with U.S. GAAP, the fair value determination involves management judgment in determining the significant estimates and assumptions used and was made using existing regulatory conditions for net assets associated with Suncadia Water Company, LLC and T&W Water Service Company. We consider the preliminary purchase price allocation incomplete for Suncadia Environmental Company, LLC as information relevant to determining an estimated fair value was not available at the time the acquisition closed or as of March 31, 2020 . Under these circumstances, the preliminary valuation was based on the books and records received from the seller. As a result, subsequent adjustments to the preliminary valuation of tangible assets, contract assets and liabilities, tax positions, and goodwill will likely be required. Subsequent adjustments are not expected to be significant, and any such adjustments are expected to be completed within the one-year measurement period for all acquisitions described above. Total preliminary goodwill of $19.1 million was recognized from the acquisitions described above. No intangible assets aside from goodwill were acquired. The goodwill recognized is attributable to the regulated water utility service territories, experienced workforces, and the strategic benefits from both the water and wastewater utilities expected from growth in their service territories. The total amount of goodwill that is expected to be deductible for income tax purposes is approximately $17.0 million . The acquisition costs associated with each business combination were expensed as incurred. The results of these business combinations were not material to the consolidated financial results of NW Holdings for the three months ended March 31, 2020 . 2019 Business Combinations Sunriver On May 31, 2019 , NWN Water of Oregon, a wholly-owned indirect subsidiary of NW Holdings, completed the acquisition of Sunriver Water, LLC and Sunriver Environmental, LLC (collectively referred to as Sunriver), a privately-owned water utility and wastewater treatment company located in Sunriver, Oregon that serves approximately 9,400 connections. The acquisition-date fair value of the total consideration transferred, after closing adjustments, was approximately $55.0 million in cash consideration. The transaction aligns with NW Holdings' water sector strategy as it continues to expand its water utility service territory in the Pacific Northwest and begins to pursue wastewater investment opportunities. The Sunriver acquisition met the criteria of a business combination, and as such a preliminary allocation of the consideration to the acquired assets based on their estimated fair value as of the acquisition date was performed. In accordance with U.S. GAAP, the fair value determination was made using existing regulatory conditions for assets associated with Sunriver Water, LLC as well as existing market conditions and standard valuation approaches for assets associated with Sunriver Environmental, LLC in order to allocate value as determined by an independent third party assessor for certain assets, which involved the use of management judgment in determining the significant estimates and assumptions used by the assessor, with the remaining difference from the consideration transferred being recorded as goodwill. This allocation is considered preliminary as of March 31, 2020 , as facts and circumstances that existed as of the acquisition date may be discovered as we continue to integrate Sunriver. As a result, subsequent adjustments to the preliminary valuation of tangible assets, tax positions, and goodwill may be required. Subsequent adjustments are not expected to be significant, and any such adjustments are expected to be completed within the one-year measurement period. The acquisition costs were expensed as incurred. Preliminary goodwill of $40.4 million was recognized from this acquisition. The goodwill recognized is attributable to Sunriver's regulated water utility service territory, experienced workforce, and the strategic benefits for both the water utility and wastewater services expected from growth in its service territory. No intangible assets aside from goodwill were acquired. The total amount of goodwill that is expected to be deductible for income tax purposes is approximately $50.2 million . The preliminary purchase price for the acquisition has been allocated to the net assets acquired as of the acquisition date and is as follows: In thousands May 31, 2019 Current assets $ 222 Property, plant and equipment 13,565 Goodwill 40,355 Deferred tax assets 828 Current liabilities (22 ) Total net assets acquired $ 54,948 The amount of Sunriver revenues included in NW Holdings' consolidated statements of comprehensive income is $1.5 million for the three months ended March 31, 2020 . Earnings from Sunriver operations for the three months ended March 31, 2020 were not material to the results of NW Holdings. Other Business Combinations During 2019, NWN Water completed three additional acquisitions qualifying as business combinations. The aggregate fair value of the preliminary consideration transferred for these acquisitions was approximately $2.0 million . These business combinations were not significant to NW Holdings' results of operations. Goodwill NW Holdings allocates 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, total goodwill was $69.2 million as of March 31, 2020 , $9.0 million as of March 31, 2019 and $49.9 million as of December 31, 2019 . The increase in the goodwill balance was primarily due to additions associated with our acquisitions in the water sector. All of our goodwill is related to water and wastewater acquisitions and is included in the other category for segment reporting purposes. 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, 2020
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 2020 2019 2019 Natural gas (in therms): Financial 487,420 255,550 651,540 Physical 369,450 422,825 512,849 Foreign exchange $ 9,885 $ 7,241 $ 6,650 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 the weighted-average cost of gas in the PGA filing. Rates and hedging approaches may vary between states due to different rate structures and mechanisms. 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 2019-20 and 2018-19 gas years with forecasted sales volumes hedged at 52% and 48% in financial swap and option contracts, and 19% and 24% in physical gas supplies, respectively. Hedge contracts entered into prior to the PGA filing in September 2019 were included in the PGA for the 2019-20 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, 2020 2019 In thousands Natural gas commodity Foreign exchange Natural gas commodity Foreign exchange Benefit (expense) to cost of gas $ (5,343 ) $ (466 ) $ 7,007 $ (89 ) Operating revenues (expense) (2,433 ) — 2,367 — Amounts deferred to regulatory accounts on balance sheet 7,405 466 (9,029 ) 89 Total gain (loss) in pre-tax earnings $ (371 ) $ — $ 345 $ — 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 losses of $2.1 million for the three months ended March 31, 2020 , from the settlement of natural gas financial derivative contracts, whereas, net gains of $11.3 million were realized for the three months ended March 31, 2019 . Realized gains and losses offset the higher or lower cost of gas purchased with differences refunded to or collected from customers in the following year through the PGA. Credit Risk Management of Financial Derivatives Instruments No collateral was posted with or by NW Natural counterparties as of March 31, 2020 or 2019 . NW Natural attempts to minimize the potential exposure to collateral calls by diversifying 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 2020 or 2019 . 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. If credit-risk related contingent features within these contracts were triggered as of March 31, 2020 , assuming current current gas prices and a credit rating downgrade to a speculative level, we could have been required to post $2.1 million in collateral calls, including estimates for adequate assurance. 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. NW Natural’s current commodity financial swap and option contracts outstanding reflect unrealized losses of $0.2 million at March 31, 2020 and unrealized losses of $0.5 million at March 31, 2019 . If netted by counterparty, NW Natural's physical and financial derivative position would result in an asset of $3.0 million and a liability of $4.3 million as of March 31, 2020 , an asset of $ 6.4 million and a liability of $ 2.0 million as of March 31, 2019 , and an asset of $9.4 million and a liability of $1.9 million as of December 31, 2019 . NW Natural is exposed to derivative credit and liquidity risk primarily through securing fixed price natural gas commodity swaps with financial counterparties. NW Natural utilizes master netting arrangements through International Swaps and Derivatives Association contracts to minimize this risk along with collateral support agreements with counterparties based on their credit ratings. In certain cases, NW Natural requires guarantees or letters of credits from counterparties to meet its minimum credit requirement standards. See Note 16 in the 2019 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, 2020 . Using significant other observable or Level 2 inputs, the net fair value was a liability of $ 1.3 million , an asset of $ 4.4 million , and an asset of $7.5 million as of March 31, 2020 and 2019 , and December 31, 2019 , 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, 2020 and 2019 . See Note 2 in the 2019

Environmental Matters

Environmental Matters	3 Months Ended
	Mar. 31, 2020
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 recovery mechanisms in place to collect 96.68% of remediation costs allocable to Oregon customers and 3.32% of costs allocable to Washington customers. 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 2020 2019 2019 2020 2019 2019 Portland Harbor site: Gasco/Siltronic Sediments $ 11,829 $ 4,595 $ 11,632 $ 42,837 $ 44,427 $ 46,082 Other Portland Harbor 2,554 2,299 2,543 6,574 5,958 6,920 Gasco/Siltronic Upland site 12,822 11,951 14,203 42,833 43,800 43,616 Central Service Center site — 10 — — — — Front Street site 10,704 11,288 10,847 — — — Oregon Steel Mills — — — 179 179 179 Total $ 37,909 $ 30,143 $ 39,225 $ 92,423 $ 94,364 $ 96,797 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, each jointly and severally liable, at 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 one hundred PRPs. NW Natural is 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; accordingly, NW Natural has not modified any of the recorded liabilities at this time as a result of the issuance of the Portland Harbor ROD. NW Natural manages its 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. In March 2020, NW Natural and the EPA amended the Administrative Order on Consent to include additional remedial design activities downstream of the Gasco sediments site and in the navigation channel. Siltronic Corporation is not a party to the amended order. 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 cleanup range from $54.7 million to $350 million . NW Natural has recorded a liability of $54.7 million for the Gasco sediment clean-up, which reflects the low end of the range. At this time, we believe sediments at the Gasco sediments site represent the largest portion of NW Natural's 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 remedial design and cleanup 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. On the motion of NW Natural and certain other defendants the federal court has stayed the case pending the outcome of the non-binding allocation proceeding discussed above. 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 Cleanup 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 Remedial Assessment (RA) for this site, 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. The investigative phase to characterize the existing site has been completed and determined by the Oregon Department of Environmental Quality (DEQ) to be sufficient to allow for the issuance of a Conditional No Further Action (cNFA). NW Natural is now conducting ongoing environmental monitoring activities over the next 5 years in order to meet the conditions which were included within the cNFA . 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 its estimate of the remaining cost to construct the remedy in the first quarter of 2020 to approximately $9.8 million . Further, NW Natural has recognized an additional liability of $0.9 million for design costs, regulatory and permitting issues, and post-construction work. NW Natural currently plans to construct the remedy in 2020. Oregon Steel Mills site. Refer to " Legal Proceedings" below. Environmental Cost Deferral and Recovery NW Natural has authorizations in Oregon and Washington to defer costs related to remediation of properties that are owned or were previously owned by NW Natural. In Oregon, a Site Remediation and Recovery Mechanism (SRRM) is currently in place to recover prudently incurred costs allocable to Oregon customers, subject to an earnings test. On October 21, 2019 the WUTC authorized an Environmental Cost Recovery Mechanism (ECRM) for recovery of prudently incurred costs allocable to Washington customers beginning November 1, 2019 . See Note 18 in the 2019 Form 10-K for a description of SRRM and ECRM collection processes. The following table presents information regarding the total regulatory asset deferred: March 31, December 31, In thousands 2020 2019 2019 Deferred costs and interest (1) $ 37,586 $ 36,874 $ 36,673 Accrued site liabilities (2) 129,977 124,133 135,662 Insurance proceeds and interest (80,613 ) (89,305 ) (79,949 ) Total regulatory asset deferral (1) $ 86,950 $ 71,702 $ 92,386 Current regulatory assets (3) 4,459 5,090 4,762 Long-term regulatory assets (3) 82,491 66,612 87,624 (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 2020 and $0.4 million in 2019 , 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, neither the cash paid nor insurance proceeds received accrue a carrying charge. 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 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. Legal Proceedings 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 including the matters discussed above and ordinary course claims and litigation noted below. 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 18 in the 2019 Form 10-K. For additional information regarding other commitments and contingencies, see Note 17 in the 2019 Form 10-K.

Discontinued Operations

Discontinued Operations	3 Months Ended
	Mar. 31, 2020
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 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. The sale of Gill Ranch was approved by the CPUC in December 2019, and the transaction is subject to other customary closing conditions and covenants, including the requirement that all of the representations and warranties be true and correct as of the closing date except, as would not, in the case of certain representations and warranties, be reasonably expected to have a material adverse effect on Gill Ranch. The Agreement, as amended, was subject to termination by either party if the transaction had not closed by March 31, 2020. On March 20, 2020, NWN Gas Storage and the buyer amended the Agreement to change the date after which the Agreement would be subject to termination by either party from March 31, 2020 to May 15, 2020. 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 2020 2019 2019 Assets: Accounts receivable $ 514 $ 1,277 $ 333 Inventories 689 627 695 Other current assets 386 337 457 Property, plant, and equipment 13,349 12,033 13,291 Less: Accumulated depreciation 7 7 7 Operating lease right of use asset 118 118 118 Other non-current assets 247 247 247 Total discontinued operations assets - current assets (1) $ 15,296 $ 14,632 $ 15,134 Liabilities: Accounts payable $ 717 $ 1,102 $ 1,250 Other current liabilities 553 359 848 Operating lease liabilities 110 111 116 Other non-current liabilities 11,421 11,710 11,495 Total discontinued operations liabilities - current liabilities (1) $ 12,801 $ 13,282 $ 13,709 (1) The total assets and liabilities of Gill Ranch are classified as current as of the periods presented above 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: Three Months Ended March 31, In thousands, except per share data 2020 2019 Revenues $ 908 $ 1,721 Expenses: Operations and maintenance 1,580 1,613 General taxes 47 59 Depreciation and amortization 106 106 Other expenses and interest 231 237 Total expenses 1,964 2,015 Loss from discontinued operations before income taxes (1,056 ) (294 ) Income tax benefit (278 ) (77 ) Loss from discontinued operations, net of tax $ (778 ) $ (217 ) Loss from discontinued operations per share of common stock: Basic $ (0.02 ) $ (0.01 ) Diluted $ (0.02 ) $ (0.01 )

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2020
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), Idaho Public Utilities Commission (IPUC) or Public Utility Commission of Texas (PUCT), 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 Holdings' or NW Natural's consolidated financial position or results of operations. Recently Adopted Accounting Pronouncements 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 requires 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 were effective beginning January 1, 2020 and were applied with modified retrospective methodology. The adoption of this ASU did not materially affect the financial statements and disclosures of NW Holdings or NW Natural. The majority of NW Holdings' and NW Natural's financial assets are either short-term in nature, such as trade receivables, or relate to leased gas facilities under approved rate schedules. Allowance for trade receivables. Accounts receivable consist primarily of amounts due for natural gas sales and transportation services to NGD customers and amounts due for gas storage services. The payment term of these receivables is generally 15 days. NW Holdings and NW Natural establish allowances for uncollectible accounts (allowance) for trade receivables, including accrued unbilled revenue, based on customer types that share similar risk characteristics: residential, commercial, and industrial. For these short-term receivables, it is not expected that forecasted economic conditions would significantly affect the loss estimates under stable economic conditions. For extreme situations like a financial crisis, natural disaster, and the economic slowdown caused by pandemics like COVID-19, we enhance our review and analysis. Please refer to the section on COVID-19 impact below for more discussion. COVID-19 Impact. COVID-19, which was declared a pandemic by the World Health Organization in March 2020, has resulted in widespread global, national and local effects. On March 23, 2020, the Governors of Oregon and Washington, the states in which NW Natural’s service territories are located, issued stay at home executive orders. These and subsequent executive orders required the closure of “non-essential” businesses and permitted the continuation of “essential services.” As a result of these measures, NW Natural issued a notification in mid-March that it would not charge late payment fees or disconnect customers for late payment. Furthermore, we suspended sending outstanding receivable balances to collections. After taking into the consideration the significant exposure to quarantine-related job losses in Oregon and Washington state, NW Holdings and NW Natural looked beyond our standard review procedures for our allowance for uncollectible accounts calculation, including analyzing the significant indications of unemployment rate and comparing to historic economic data during the 2007-2009 time period where the country experienced an economic recession. We then considered other qualitative information including data from our call center such as recent trends in credit-related calls. We also reviewed statistics from our website for increases in credit-related inquiries. Finally, we considered the economic stimulus provided by the federal government which could have a beneficial impact on residential and commercial customers' abilities to ultimately make payment on their accounts. Taking all of these factors into consideration, we concluded a reasonable adjustment to the uncollectible provision for customer accounts as of March 31, 2020 would be a 50% increase in net write-offs as a percentage of gas sales for residential and small commercial customers. Our method for estimating our industrial provision for uncollectible accounts remains the same as the level of accounts receivable was lower due to reduced demand in the first quarter of 2020. The following table presents the activity related to the NW Holdings provision for uncollectible accounts by pool, substantially all of which is related to NW Natural's accounts receivable: As of As of January 1, 2020 Three Months Ended March 31, 2020 March 31, 2020 In thousands Beginning Balance Provision recorded Write-offs recognized Write-offs recovered Ending Balance Allowance for uncollectible accounts related to accounts receivable: Residential $ 432 $ 445 $ 6 $ — $ 883 Commercial 57 220 — (34 ) 243 Industrial 72 27 — (1 ) 98 Accrued unbilled and other 112 2 — (3 ) 111 Total $ 673 $ 694 $ 6 $ (38 ) $ 1,335 Allowance for net investments in sales-type leases. NW Natural currently holds two net investments in sales-type leases, with substantially all of the net investment balance related to the North Mist natural gas storage agreement with Portland General Electric (PGE) which is billed under an OPUC-approved rate schedule. See Note 6 for more information on the North Mist lease. Due to the nature of this service, PGE may recover the costs of the lease through general rate cases. Therefore, we expect the risk of loss due to the credit of this lessee to be very low. As such, no allowance for uncollectibility was recorded for our sales-type lease receivables. NW Natural will continue monitoring the credit health of the lessees and the overall economic environment, including the economic factors closely tied to the financial health of our current and future lessees. 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 were effective for us beginning January 1, 2020. 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. NW Holdings and NW Natural do not have either Level 3 fair value measurements or transfers between Level 1 or Level 2 in their current portfolios. The adoption did not have an impact on the financial statements or disclosures of NW Holdings or NW Natural. 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 were effective for us beginning January 1, 2020 and were applied retrospectively. The adoption of this ASU did not materially affect the financial statements and disclosures of NW Holdings or NW Natural. 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. 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. Recently Issued Accounting Pronouncements INCOME TAXES. On December 18, 2019, the FASB issued ASU 2019-12, "Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes." The purpose of the amendment is to reduce cost and complexity related to accounting for income taxes by removing certain exceptions to the general principles and improving consistent application for other areas in Topic 740. The amendments in this update are effective for us beginning January 1, 2021. Early adoption is permitted. The amended presentation and disclosure guidance should be applied retrospectively. We do not expect this ASU to materially affect the financial statements and disclosures of NW Holdings or NW Natural. REFERENCE RATE REFORM. On March 12, 2020, the FASB issued ASU 2020-04, "Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting." The purpose of the amendment is to provide optional expedients and exceptions for applying generally accepted accounting principles (GAAP) to contracts, hedging relationships, and other transactions affected by reference rate reform if certain criteria are met. The amendments in this Update apply only to contracts, hedging relationships, and other transactions that reference LIBOR or another reference rate expected to be discontinued because of reference rate reform. The amendments in this Update are effective for all entities as of March 12, 2020 through December 31, 2022. We do not expect this ASU to materially affect the financial statements and disclosures of NW Holdings or NW Natural.

Significant Accounting Polici_3

Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
Accounts Receivable, Allowance for Credit Loss [Table Text Block]	The following table presents the activity related to the NW Holdings provision for uncollectible accounts by pool, substantially all of which is related to NW Natural's accounts receivable: As of As of January 1, 2020 Three Months Ended March 31, 2020 March 31, 2020 In thousands Beginning Balance Provision recorded Write-offs recognized Write-offs recovered Ending Balance Allowance for uncollectible accounts related to accounts receivable: Residential $ 432 $ 445 $ 6 $ — $ 883 Commercial 57 220 — (34 ) 243 Industrial 72 27 — (1 ) 98 Accrued unbilled and other 112 2 — (3 ) 111 Total $ 673 $ 694 $ 6 $ (38 ) $ 1,335
Schedule of Regulatory Assets	Amounts deferred as regulatory assets and liabilities for NW Holdings and NW Natural were as follows: Regulatory Assets March 31, December 31, In thousands 2020 2019 2019 NW Natural: Current: Unrealized loss on derivatives (1) $ 4,845 $ 2,845 $ 2,000 Gas costs 10,898 17,927 20,140 Environmental costs (2) 4,459 5,090 4,762 Decoupling (3) 610 3,937 1,969 Pension balancing (4) 6,794 4,955 5,939 Income taxes 3,576 2,209 2,209 Other (5) 6,633 9,354 4,910 Total current $ 37,815 $ 46,317 $ 41,929 Non-current: Unrealized loss on derivatives (1) $ 939 $ 1,161 $ 609 Pension balancing (4) 46,031 50,408 48,251 Income taxes 16,354 17,758 17,173 Pension and other postretirement benefit liabilities 168,676 171,565 173,262 Environmental costs (2) 82,491 66,612 87,624 Gas costs 350 8,919 2,866 Decoupling (3) — 250 — Other (5) 13,183 10,521 13,361 Total non-current $ 328,024 $ 327,194 $ 343,146
Schedule of Regulatory Liabilities	Regulatory Liabilities March 31, December 31, In thousands 2020 2019 2019 NW Natural: Current: Gas costs $ 4,046 $ 11,126 $ 1,223 Unrealized gain on derivatives (1) 2,257 7,284 6,622 Decoupling (3) 11,203 2,055 4,831 Income taxes 7,522 7,763 8,435 Other (5) 22,109 18,542 23,546 Total current $ 47,137 $ 46,770 $ 44,657 Non-current: Gas costs $ 1,328 $ 1,421 $ 2,013 Unrealized gain on derivatives (1) 2,451 541 3,337 Decoupling (3) 4,784 614 6,378 Income taxes (6) 192,644 202,692 198,219 Accrued asset removal costs (7) 408,212 384,702 401,893 Other (5) 12,956 10,728 13,877 Total non-current - NW Natural $ 622,375 $ 600,698 $ 625,717 Other (NW Holdings) 844 — — Total non-current - NW Holdings $ 623,219 $ 600,698 $ 625,717 (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, 2020
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 2020 2019 Net income from continuing operations $ 48,276 $ 43,418 Loss from discontinued operations, net of tax (778 ) (217 ) Net income $ 47,498 $ 43,201 Average common shares outstanding - basic 30,491 28,906 Additional shares for stock-based compensation plans (See Note 7) 44 64 Average common shares outstanding - diluted 30,535 28,970 Earnings from continuing operations per share of common stock: Basic $ 1.58 $ 1.50 Diluted $ 1.58 $ 1.50 Loss from discontinued operations per share of common stock: Basic $ (0.02 ) $ (0.01 ) Diluted $ (0.02 ) $ (0.01 ) Earnings per share of common stock: Basic $ 1.56 $ 1.49 Diluted $ 1.56 $ 1.49 Additional information: Anti-dilutive shares 3 5

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2020
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, by Segment	The following table presents summary financial information concerning the reportable segment and other 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 2020 Operating revenues $ 278,487 $ 4,042 $ 282,529 $ 2,622 $ 285,151 Depreciation and amortization 23,946 244 24,190 485 24,675 Income (loss) from operations 75,258 1,763 77,021 (575 ) 76,446 Net income (loss) from continuing operations 47,943 1,236 49,179 (903 ) 48,276 Capital expenditures 56,157 77 56,234 1,212 57,446 Total assets at March 31, 2020 (1) 3,776,650 48,746 3,825,396 160,835 3,986,231 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 Total assets at December 31, 2019 (1) 3,273,835 47,652 3,321,487 91,833 3,413,320 (1) Total assets for NW Holdings exclude assets related to discontinued operations of $15.3 million , $14.6 million , and $15.1 million as of March 31, 2020 , March 31, 2019 , and December 31, 2019 , respectively.
NGD Margin	The following table presents additional segment information concerning NGD margin: Three Months Ended March 31, In thousands 2020 2019 NGD margin calculation: NGD distribution revenues $ 273,561 $ 278,983 Other regulated services 4,926 58 Total NGD operating revenues 278,487 279,041 Less: NGD cost of gas 108,595 105,513 Environmental remediation 4,005 8,947 Revenue taxes 11,743 11,926 NGD margin $ 154,144 $ 152,655

Revenue (Tables)

Revenue (Tables)	3 Months Ended
	Mar. 31, 2020
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	The following tables present disaggregated revenue from continuing operations: Three Months Ended March 31, In thousands NGD Other (NW Natural) NW Natural Other (NW Holdings) NW Holdings 2020 Natural gas sales $ 274,004 $ — $ 274,004 $ — $ 274,004 Gas storage revenue, net — 2,336 2,336 — 2,336 Asset management revenue, net — 150 150 — 150 Appliance retail center revenue — 1,556 1,556 — 1,556 Other revenue 337 — 337 2,622 2,959 Revenue from contracts with customers 274,341 4,042 278,383 2,622 281,005 Alternative revenue (472 ) — (472 ) — (472 ) Leasing revenue 4,618 — 4,618 — 4,618 Total operating revenues $ 278,487 $ 4,042 $ 282,529 $ 2,622 $ 285,151 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

Leases (Tables)

Leases (Tables)	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2018
Leases [Abstract]
Lease Revenue	The components of lease revenue at NW Natural were as follows: Three Months Ended March 31, In thousands 2020 2019 Lease revenue Operating leases $ 28 $ 48 Sales-type leases 4,590 60 Total lease revenue $ 4,618 $ 108
Lessor, Operating Lease, Payments to be Received, Maturity	Total future minimum lease payments to be received under non-cancellable leases at NW Natural at March 31, 2020 are as follows: In thousands Operating Sales-Type Total Remainder of 2020 $ 56 $ 13,603 $ 13,659 2021 49 17,518 17,567 2022 45 17,026 17,071 2023 45 16,557 16,602 2024 45 15,867 15,912 Thereafter 94 266,563 266,657 Total lease revenue $ 334 $ 347,134 $ 347,468 Less: imputed interest 199,041 Total leases receivable $ 148,093
Lease Expense	The components of lease expense, a portion of which is capitalized, were as follows: Three Months Ended March 31, In thousands 2020 2019 NW Natural: Operating lease expense $ 1,202 1,142 Short-term lease expense 198 160 Other (NW Holdings): Operating lease expense $ 52 46 Short-term lease expense — — NW Holdings: Operating lease expense $ 1,254 1,188 Short-term lease expense 198 160
Operating Lease, Lease Asset and Liabilities	Supplemental balance sheet information related to operating leases as of March 31, 2020 is as follows: In thousands March 31, December 31, 2020 2019 2019 NW Natural: Operating lease right of use asset $ 79,383 $ 5,903 $ 2,760 Operating lease liabilities - current liabilities $ 984 $ 4,477 $ 1,979 Operating lease liabilities - non-current liabilities 79,052 1,413 772 Total operating lease liabilities $ 80,036 $ 5,890 $ 2,751 Other (NW Holdings): Operating lease right of use asset $ 139 $ 260 $ 190 Operating lease liabilities - current liabilities $ 87 $ 179 $ 122 Operating lease liabilities - non-current liabilities 53 82 69 Total operating lease liabilities $ 140 $ 261 $ 191 NW Holdings: Operating lease right of use asset $ 79,522 $ 6,163 $ 2,950 Operating lease liabilities - current liabilities $ 1,071 $ 4,656 $ 2,101 Operating lease liabilities - non-current liabilities 79,105 1,495 841 Total operating lease liabilities $ 80,176 $ 6,151 $ 2,942
Operating Lease, Weighted Average Remaining Term and Discount Rates [Table Text Block]	The weighted-average remaining lease terms and weighted-average discount rates for the operating leases at NW Natural were as follows: In thousands March 31, December 31, 2020 2019 2019 Weighted-average remaining lease term (years) 19.7 1.3 1.0 Weighted-average discount rate 7.20 % 3.79 % 3.98 %
Lessee, Operating Lease, Liability, Maturity		Maturities of operating lease liabilities at March 31, 2020 were as follows: In thousands NW Natural Other NW Holdings Remainder of 2020 $ 3,117 $ 74 $ 3,191 2021 6,726 52 6,778 2022 6,848 18 6,866 2023 6,983 — 6,983 2024 7,146 — 7,146 Thereafter 130,935 — 130,935 Total lease payments 161,755 144 161,899 Less: imputed interest 81,719 4 81,723 Total lease obligations 80,036 140 80,176 Less: current obligations 984 87 1,071 Long-term lease obligations $ 79,052 $ 53 $ 79,105
Lessee, Leases, Supplemental Cash Flow Information	Cash Flow Information Supplemental cash flow information related to leases was as follows: Three Months Ended March 31, In thousands 2020 2019 NW Natural: Cash paid for amounts included in the measurement of lease liabilities Operating cash flows from operating leases $ 1,196 $ 1,091 Finance cash flows from finance leases 155 — Right of use assets obtained in exchange for lease obligations Operating leases $ 77,988 $ 6,987 Finance leases 233 — Other (NW Holdings): Cash paid for amounts included in the measurement of lease liabilities Operating cash flows from operating leases $ 52 $ 43 Right of use assets obtained in exchange for lease obligations Operating leases $ — $ 304 NW Holdings: Cash paid for amounts included in the measurement of lease liabilities Operating cash flows from operating leases $ 1,248 $ 1,134 Finance cash flows from finance leases 155 — Right of use assets obtained in exchange for lease obligations Operating leases $ 77,988 $ 7,291 Finance leases 233 —

Debt (Tables)

Debt (Tables)	3 Months Ended
	Mar. 31, 2020
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 Holdings' long-term debt, including current maturities of long-term debt, using market prices in effect on the valuation date: NW Holdings March 31, December 31, In thousands 2020 2019 2019 Gross long-term debt $ 961,718 $ 741,888 $ 886,776 Unamortized debt issuance costs (7,554 ) (5,246 ) (5,712 ) Carrying amount $ 954,164 $ 736,642 $ 881,064 Estimated fair value (1) $ 1,038,691 $ 777,778 $ 957,268 (1) Estimated fair value does not include unamortized debt issuance costs. 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: NW Natural March 31, December 31, In thousands 2020 2019 2019 Gross long-term debt $ 924,700 $ 739,700 $ 849,700 Unamortized debt issuance costs (7,554 ) (5,246 ) (5,712 ) Carrying amount $ 917,146 $ 734,454 $ 843,988 Estimated fair value (1) $ 1,001,058 $ 775,590 $ 919,835 (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, 2020
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 2020 2019 2020 2019 Service cost $ 1,657 $ 1,517 $ 64 $ 68 Interest cost 4,011 4,662 223 281 Expected return on plan assets (5,496 ) (5,207 ) — — Amortization of prior service costs — 2 (117 ) (117 ) Amortization of net actuarial loss 4,778 3,603 143 97 Net periodic benefit cost 4,950 4,577 313 329 Amount allocated to construction (668 ) (586 ) (23 ) (24 ) Net periodic benefit cost charged to expense 4,282 3,991 290 305 Regulatory pension disallowance — 10,500 — — Amortization of regulatory balancing account 2,801 12,511 — — Net amount charged to expense $ 7,083 $ 27,002 $ 290 $ 305
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 2020 2019 Beginning balance $ (10,733 ) $ (7,188 ) Amounts reclassified from AOCL: Amortization of actuarial losses 218 156 Reclassification of stranded tax effects (1) — (1,366 ) Total reclassifications before tax 218 (1,210 ) Tax (benefit) expense (58 ) (41 ) Total reclassifications for the period 160 (1,251 ) Ending balance $ (10,573 ) $ (8,439 ) (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, 2020
Income Tax Disclosure [Abstract]
Schedule of Effective Income Tax Rate Reconciliation	The effective income tax rate varied from the federal statutory rate due to the following: Three Months Ended March 31, NW Holdings NW Natural In thousands 2020 2019 2020 2019 Income tax at statutory rate (federal) $ 13,105 $ 11,022 $ 13,355 $ 11,159 State 3,677 3,291 3,737 3,326 Increase (decrease): Differences required to be flowed-through by regulatory commissions (2,525 ) (5,260 ) (2,525 ) (5,260 ) Other, net (130 ) (378 ) (149 ) (377 ) Total provision for income taxes on continuing operations $ 14,127 $ 8,675 $ 14,418 $ 8,848 Effective income tax rate for continuing operations 22.8 % 16.7 % 22.8 % 16.8 %

Property, Plant and Equipment_2

Property, Plant and Equipment (Tables)	3 Months Ended
	Mar. 31, 2020
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 2020 2019 2019 NW Natural: NGD plant in service $ 3,344,345 $ 3,159,754 $ 3,302,049 NGD work in progress 95,566 204,938 84,965 Less: Accumulated depreciation 1,030,234 985,961 1,017,931 NGD plant, net 2,409,677 2,378,731 2,369,083 Other plant in service 64,314 65,283 63,513 Other construction work in progress 4,824 5,329 5,548 Less: Accumulated depreciation 18,901 18,851 18,662 Other plant, net 50,237 51,761 50,399 Total property, plant, and equipment $ 2,459,914 $ 2,430,492 $ 2,419,482 Other (NW Holdings): Other plant in service $ 42,016 $ 4,156 $ 20,671 Less: Accumulated depreciation 1,715 305 1,254 Other plant, net $ 40,301 $ 3,851 $ 19,417 NW Holdings: Total property, plant, and equipment $ 2,500,215 $ 2,434,343 $ 2,438,899 NW Natural and NW Holdings: Capital expenditures in accrued liabilities $ 33,999 $ 25,035 $ 32,502

Gas Reserves (Tables)

Gas Reserves (Tables)	3 Months Ended
	Mar. 31, 2020
Gas Reserves [Abstract]
Gas Reserves	The following table outlines NW Natural's net gas reserves investment: March 31, December 31, In thousands 2020 2019 2019 Gas reserves, current $ 14,351 $ 16,157 $ 15,278 Gas reserves, non-current 172,956 171,150 172,029 Less: Accumulated amortization 127,722 109,243 123,635 Total gas reserves (1) 59,585 78,064 63,672 Less: Deferred taxes on gas reserves 14,522 19,638 15,515 Net investment in gas reserves $ 45,063 $ 58,426 $ 48,157 (1) The net investment in additional wells included in total gas reserves was $ 3.6 million , $ 4.5 million and $ 3.8 million at March 31, 2020 and 2019 and December 31, 2019

Business Combinations Busines_2

Business Combinations Business Combinations (Tables)	3 Months Ended
	Mar. 31, 2020
Business Combinations [Abstract]
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block]	The preliminary purchase price for the acquisition has been allocated to the net assets acquired as of the acquisition date and is as follows: In thousands May 31, 2019 Current assets $ 222 Property, plant and equipment 13,565 Goodwill 40,355 Deferred tax assets 828 Current liabilities (22 ) Total net assets acquired $ 54,948

Derivative Instruments (Tables)

Derivative Instruments (Tables)	3 Months Ended
	Mar. 31, 2020
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 2020 2019 2019 Natural gas (in therms): Financial 487,420 255,550 651,540 Physical 369,450 422,825 512,849 Foreign exchange $ 9,885 $ 7,241 $ 6,650
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, 2020 2019 In thousands Natural gas commodity Foreign exchange Natural gas commodity Foreign exchange Benefit (expense) to cost of gas $ (5,343 ) $ (466 ) $ 7,007 $ (89 ) Operating revenues (expense) (2,433 ) — 2,367 — Amounts deferred to regulatory accounts on balance sheet 7,405 466 (9,029 ) 89 Total gain (loss) in pre-tax earnings $ (371 ) $ — $ 345 $ —

Environmental Matters (Tables)

Environmental Matters (Tables)	3 Months Ended
	Mar. 31, 2020
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 2020 2019 2019 2020 2019 2019 Portland Harbor site: Gasco/Siltronic Sediments $ 11,829 $ 4,595 $ 11,632 $ 42,837 $ 44,427 $ 46,082 Other Portland Harbor 2,554 2,299 2,543 6,574 5,958 6,920 Gasco/Siltronic Upland site 12,822 11,951 14,203 42,833 43,800 43,616 Central Service Center site — 10 — — — — Front Street site 10,704 11,288 10,847 — — — Oregon Steel Mills — — — 179 179 179 Total $ 37,909 $ 30,143 $ 39,225 $ 92,423 $ 94,364 $ 96,797
Environmental Regulatory Table	The following table presents information regarding the total regulatory asset deferred: March 31, December 31, In thousands 2020 2019 2019 Deferred costs and interest (1) $ 37,586 $ 36,874 $ 36,673 Accrued site liabilities (2) 129,977 124,133 135,662 Insurance proceeds and interest (80,613 ) (89,305 ) (79,949 ) Total regulatory asset deferral (1) $ 86,950 $ 71,702 $ 92,386 Current regulatory assets (3) 4,459 5,090 4,762 Long-term regulatory assets (3) 82,491 66,612 87,624 (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 2020 and $0.4 million in 2019 , 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, neither the cash paid nor insurance proceeds received accrue a carrying charge. 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, 2020
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 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. The sale of Gill Ranch was approved by the CPUC in December 2019, and the transaction is subject to other customary closing conditions and covenants, including the requirement that all of the representations and warranties be true and correct as of the closing date except, as would not, in the case of certain representations and warranties, be reasonably expected to have a material adverse effect on Gill Ranch. The Agreement, as amended, was subject to termination by either party if the transaction had not closed by March 31, 2020. On March 20, 2020, NWN Gas Storage and the buyer amended the Agreement to change the date after which the Agreement would be subject to termination by either party from March 31, 2020 to May 15, 2020. 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 2020 2019 2019 Assets: Accounts receivable $ 514 $ 1,277 $ 333 Inventories 689 627 695 Other current assets 386 337 457 Property, plant, and equipment 13,349 12,033 13,291 Less: Accumulated depreciation 7 7 7 Operating lease right of use asset 118 118 118 Other non-current assets 247 247 247 Total discontinued operations assets - current assets (1) $ 15,296 $ 14,632 $ 15,134 Liabilities: Accounts payable $ 717 $ 1,102 $ 1,250 Other current liabilities 553 359 848 Operating lease liabilities 110 111 116 Other non-current liabilities 11,421 11,710 11,495 Total discontinued operations liabilities - current liabilities (1) $ 12,801 $ 13,282 $ 13,709 (1) The total assets and liabilities of Gill Ranch are classified as current as of the periods presented above 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: Three Months Ended March 31, In thousands, except per share data 2020 2019 Revenues $ 908 $ 1,721 Expenses: Operations and maintenance 1,580 1,613 General taxes 47 59 Depreciation and amortization 106 106 Other expenses and interest 231 237 Total expenses 1,964 2,015 Loss from discontinued operations before income taxes (1,056 ) (294 ) Income tax benefit (278 ) (77 ) Loss from discontinued operations, net of tax $ (778 ) $ (217 ) Loss from discontinued operations per share of common stock: Basic $ (0.02 ) $ (0.01 ) Diluted $ (0.02 ) $ (0.01 )
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: Three Months Ended March 31, In thousands, except per share data 2020 2019 Revenues $ 908 $ 1,721 Expenses: Operations and maintenance 1,580 1,613 General taxes 47 59 Depreciation and amortization 106 106 Other expenses and interest 231 237 Total expenses 1,964 2,015 Loss from discontinued operations before income taxes (1,056 ) (294 ) Income tax benefit (278 ) (77 ) Loss from discontinued operations, net of tax $ (778 ) $ (217 ) Loss from discontinued operations per share of common stock: Basic $ (0.02 ) $ (0.01 ) Diluted $ (0.02 ) $ (0.01 )
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 2020 2019 2019 Assets: Accounts receivable $ 514 $ 1,277 $ 333 Inventories 689 627 695 Other current assets 386 337 457 Property, plant, and equipment 13,349 12,033 13,291 Less: Accumulated depreciation 7 7 7 Operating lease right of use asset 118 118 118 Other non-current assets 247 247 247 Total discontinued operations assets - current assets (1) $ 15,296 $ 14,632 $ 15,134 Liabilities: Accounts payable $ 717 $ 1,102 $ 1,250 Other current liabilities 553 359 848 Operating lease liabilities 110 111 116 Other non-current liabilities 11,421 11,710 11,495 Total discontinued operations liabilities - current liabilities (1) $ 12,801 $ 13,282 $ 13,709 (1) The total assets and liabilities of Gill Ranch are classified as current as of the periods presented above 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, 2020	Dec. 31, 2019	Mar. 31, 2019
Regulatory Assets [Line Items]
Regulatory Assets, Current	$ 37,815	$ 41,929	$ 46,317
Regulatory Assets, Noncurrent	328,024	343,146	327,194
Northwest Natural Gas Company [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	37,815	41,929	46,317
Regulatory Assets, Noncurrent	328,024	343,146	327,194
Northwest Natural Gas Company [Member] | Deferred Derivative Gain (Loss) [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	4,845	2,000	2,845
Regulatory Assets, Noncurrent	939	609	1,161
Northwest Natural Gas Company [Member] | Gas costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	10,898	20,140	17,927
Regulatory Assets, Noncurrent	350	2,866	8,919
Northwest Natural Gas Company [Member] | Environmental costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	4,459	4,762	5,090
Regulatory Assets, Noncurrent	82,491	87,624	66,612
Northwest Natural Gas Company [Member] | Decoupling [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	610	1,969	3,937
Regulatory Assets, Noncurrent	0	0	250
Northwest Natural Gas Company [Member] | Pension balancing [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	6,794	5,939	4,955
Regulatory Assets, Noncurrent	46,031	48,251	50,408
Northwest Natural Gas Company [Member] | Income taxes [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	3,576	2,209	2,209
Regulatory Assets, Noncurrent	16,354	17,173	17,758
Northwest Natural Gas Company [Member] | Pension and other postretirement benefit liabilities [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Noncurrent	168,676	173,262	171,565
Northwest Natural Gas Company [Member] | Other [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	6,633	4,910	9,354
Regulatory Assets, Noncurrent	$ 13,183	$ 13,361	$ 10,521

Significant Accounting Polici_5

Significant Accounting Policies - Regulatory Liability Disclosure (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	$ 47,137	$ 44,657	$ 46,770
Regulatory Liability, Noncurrent	623,219	625,717	600,698
COVID-19 Incremental Costs	700
COVID-19 Incremental Costs, Bad Debt	400
Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Noncurrent	844	0	0
Northwest Natural Gas Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	47,137	44,657	46,770
Regulatory Liability, Noncurrent	622,375	625,717	600,698
Northwest Natural Gas Company [Member] | Gas costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	4,046	1,223	11,126
Regulatory Liability, Noncurrent	1,328	2,013	1,421
Northwest Natural Gas Company [Member] | Deferred Derivative Gain (Loss) [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	2,257	6,622	7,284
Regulatory Liability, Noncurrent	2,451	3,337	541
Northwest Natural Gas Company [Member] | Decoupling [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	11,203	4,831	2,055
Regulatory Liability, Noncurrent	4,784	6,378	614
Northwest Natural Gas Company [Member] | Income taxes [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	7,522	8,435	7,763
Regulatory Liability, Noncurrent	192,644	198,219	202,692
Northwest Natural Gas Company [Member] | Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	22,109	23,546	18,542
Regulatory Liability, Noncurrent	12,956	13,877	10,728
Northwest Natural Gas Company [Member] | Accrued asset removal costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Noncurrent	$ 408,212	$ 401,893	$ 384,702

Significant Accounting Polici_6

Significant Accounting Policies - Credit Losses - ASU 2016-13 (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Accounts Receivable, Noncurrent, Credit Quality Indicator [Line Items]
Increase in Net Write-offs, Provision for Uncollectible Accounts, Percent	50.00%
Accounts Receivable, Allowance for Credit Loss	$ 1,335	$ 673
Accounts Receivable, Allowance for Credit Loss, Period Increase (Decrease)	694
Accounts Receivable, Allowance for Credit Loss, Writeoff	6
Accounts Receivable, Allowance for Credit Loss, Recovery	(38)
Residential [Member]
Accounts Receivable, Noncurrent, Credit Quality Indicator [Line Items]
Accounts Receivable, Allowance for Credit Loss	883	432
Accounts Receivable, Allowance for Credit Loss, Period Increase (Decrease)	445
Accounts Receivable, Allowance for Credit Loss, Writeoff	6
Accounts Receivable, Allowance for Credit Loss, Recovery	0
Commercial [Member]
Accounts Receivable, Noncurrent, Credit Quality Indicator [Line Items]
Accounts Receivable, Allowance for Credit Loss	243	57
Accounts Receivable, Allowance for Credit Loss, Period Increase (Decrease)	220
Accounts Receivable, Allowance for Credit Loss, Writeoff	0
Accounts Receivable, Allowance for Credit Loss, Recovery	(34)
Industrial [Member]
Accounts Receivable, Noncurrent, Credit Quality Indicator [Line Items]
Accounts Receivable, Allowance for Credit Loss	98	72
Accounts Receivable, Allowance for Credit Loss, Period Increase (Decrease)	27
Accounts Receivable, Allowance for Credit Loss, Writeoff	0
Accounts Receivable, Allowance for Credit Loss, Recovery	(1)
Accrued unbilled and other [Member]
Accounts Receivable, Noncurrent, Credit Quality Indicator [Line Items]
Accounts Receivable, Allowance for Credit Loss	111	$ 112
Accounts Receivable, Allowance for Credit Loss, Period Increase (Decrease)	2
Accounts Receivable, Allowance for Credit Loss, Writeoff	0
Accounts Receivable, Allowance for Credit Loss, Recovery	$ (3)

Earnings Per Share (Details)

Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Income Statement [Line Items]
Net income from continuing operations	$ 48,276	$ 43,418
Loss from discontinued operations, net of tax	(778)	(217)
Net income	$ 47,498	$ 43,201
Average common shares outstanding:
Average common shares outstanding - basic (in shares)	30,491	28,906
Additional shares for stock-based compensation plans	44	64
Average common shares outstanding - diluted (in shares)	30,535	28,970
Earnings from continuing operations per share of common stock:
Basic (in dollars per share)	$ 1.58	$ 1.50
Diluted (in dollars per share)	1.58	1.50
Loss from discontinued operations per share of common stock:
Basic (in dollars per share)	(0.02)	(0.01)
Diluted (in dollars per share)	(0.02)	(0.01)
Earnings (loss) per share of common stock
Basic (in dollars per share)	1.56	1.49
Diluted (in dollars per share)	$ 1.56	$ 1.49
Antidilutive shares	3	5
Discontinued Operations, Held-for-sale [Member] | Gill Ranch [Member]
Income Statement [Line Items]
Loss from discontinued operations, net of tax	$ (778)	$ (217)
Loss from discontinued operations per share of common stock:
Basic (in dollars per share)	$ (0.02)	$ (0.01)
Diluted (in dollars per share)	$ (0.02)	$ (0.01)

Segment Information - Narrative

Segment Information - Narrative (Details)	3 Months Ended
	Mar. 31, 2020
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, 2020	Mar. 31, 2019	Dec. 31, 2019
Segment Reporting Information [Line Items]
Operating revenues	$ 285,151	$ 285,348
Depreciation and amortization	24,675	21,572
Income from operations	76,446	76,045
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	48,276	43,418
Total assets	4,001,527	3,191,117	$ 3,428,454
Discontinued operations - total assets	15,300	14,600	15,100
Natural Gas Distribution [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	278,487	279,041
Depreciation and amortization	23,946	21,249
Income from operations	75,258	72,898
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	47,943	41,206
Capital expenditures	56,157	48,606
Total assets	3,776,650	3,091,062	3,273,835
Other Northwest Natural [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating revenues	4,042	5,805
Depreciation and amortization	244	255
Income from operations	1,763	3,746
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	1,236	2,689
Capital expenditures	77	52
Total assets	48,746	49,566	47,652
Northwest Natural Gas Company [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	282,529	284,846
Depreciation and amortization	24,190	21,504
Income from operations	77,021	76,644
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	49,179	43,895
Capital expenditures	56,234	48,658
Total assets	3,825,396	3,140,628	3,321,487
Other Northwest Holdings [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating revenues	2,622	502
Depreciation and amortization	485	68
Income from operations	(575)	(599)
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	(903)	(477)
Capital expenditures	1,212	106
Total assets	160,835	35,857	91,833
Northwest Natural Gas Company [Member]
Segment Reporting Information [Line Items]
Operating revenues	282,529	284,846
Depreciation and amortization	24,190	21,504
Income from operations	77,021	76,644
Total assets	3,825,396	3,140,628	3,321,487
Northwest Natural Gas Company [Member] | Natural Gas Distribution [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	278,487	279,041
Northwest Natural Gas Company [Member] | Other Northwest Natural [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating revenues	4,042	5,805
Northwest Natural Gas Company [Member] | Northwest Natural Gas Company [Member]
Segment Reporting Information [Line Items]
Operating revenues	282,529	284,846
Parent Company [Member]
Segment Reporting Information [Line Items]
Operating revenues	285,151	285,348
Depreciation and amortization	24,675	21,572
Income from operations	76,446	76,045
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	48,276	43,418
Capital expenditures	57,446	48,764
Total assets	$ 3,986,231	$ 3,176,485	$ 3,413,320

Segment Information - Additiona

Segment Information - Additional Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Segment Reporting Information [Line Items]
Operating revenues	$ 285,151	$ 285,348
Cost of gas	108,538	105,457
Environmental remediation	4,005	8,947
Operating Segments [Member] | Natural Gas Distribution [Member]
Segment Reporting Information [Line Items]
Natural Gas Distribution revenues	273,561	278,983
Other regulated services	4,926	58
Operating revenues	278,487	279,041
Cost of gas	108,595	105,513
Environmental remediation	4,005	8,947
Revenue taxes	11,743	11,926
NGD margin	$ 154,144	$ 152,655

Revenue - Disaggregation of Rev

Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	$ 281,005	$ 302,493
Revenues	285,151	285,348
Operating leases	28	48
Natural Gas Sales [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	274,004	296,186
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	2,336	2,783
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	150	1,506
Appliance Center Revenue [Member] | Transferred at Point in Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,556	1,516
Other revenue [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	2,959	502
Alternative revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	(472)	(17,253)
Leasing revenue [Member]
Disaggregation of Revenue [Line Items]
Operating leases	4,618	108
Northwest Natural Gas Company [Member]
Disaggregation of Revenue [Line Items]
Revenues	282,529	284,846
Northwest Natural Gas Company [Member] | Northwest Natural Gas Company [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	278,383	301,991
Revenues	282,529	284,846
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	274,004	296,186
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	2,336	2,783
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	150	1,506
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	1,556	1,516
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	337	0
Northwest Natural Gas Company [Member] | Northwest Natural Gas Company [Member] | Alternative revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	(472)	(17,253)
Northwest Natural Gas Company [Member] | Northwest Natural Gas Company [Member] | Leasing revenue [Member]
Disaggregation of Revenue [Line Items]
Operating leases	4,618	108
Operating Segments [Member] | Natural Gas Distribution [Member]
Disaggregation of Revenue [Line Items]
Revenues	278,487	279,041
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	274,341	296,186
Revenues	278,487	279,041
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	274,004	296,186
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	337	0
Operating Segments [Member] | Natural Gas Distribution [Member] | Northwest Natural Gas Company [Member] | Alternative revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	(472)	(17,253)
Operating Segments [Member] | Natural Gas Distribution [Member] | Northwest Natural Gas Company [Member] | Leasing revenue [Member]
Disaggregation of Revenue [Line Items]
Operating leases	4,618	108
Operating Segments [Member] | Northwest Natural Gas Company [Member]
Disaggregation of Revenue [Line Items]
Revenues	282,529	284,846
Corporate, Non-Segment [Member] | Other Northwest Natural [Member]
Disaggregation of Revenue [Line Items]
Revenues	4,042	5,805
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	4,042	5,805
Revenues	4,042	5,805
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	2,336	2,783
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	150	1,506
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	1,556	1,516
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	2,622	502
Revenues	2,622	502
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	2,622	502
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

Revenue - Revenue, Remaining Pe

Revenue - Revenue, Remaining Performance Obligation (Details) $ in Millions	Mar. 31, 2020USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Lessor, Sales-type Lease, Term of Contract	30 years
Lessor, Sales-type Lease, Renewal Term	50 years
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Year	9 months
Revenue, Remaining Performance Obligation, Amount	$ 12.3
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	1 year
Revenue, Remaining Performance Obligation, Amount	$ 18.2
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	1 year
Revenue, Remaining Performance Obligation, Amount	$ 14.5
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	1 year
Revenue, Remaining Performance Obligation, Amount	$ 11.6
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Year	1 year
Revenue, Remaining Performance Obligation, Amount	$ 7.8
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Year	0 years
Revenue, Remaining Performance Obligation, Amount	$ 5.3

Leases - Lease Revenue (Details

Leases - Lease Revenue (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Lessor, Lease, Description [Line Items]
Lessor, Sales-type Lease, Renewal Term	50 years
Lessor, Sales-type Lease, Term of Contract	30 years
Residual Value of Leased Asset	$ 4,100,000		$ 4,000,000
Lease Revenue [Abstract]
Operating leases	28,000	$ 48,000
Sales-type leases	4,590,000	60,000
Total lease revenue	4,618,000	$ 108,000
Operating Leases Payment to be Received [Abstract]
Operating Lease, Payments to be Received, Remainder of Fiscal Year	56,000
Operating Lease, Payments to be Received, Two Years	49,000
Operating Lease, Payments to be Received, Three Years	45,000
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	94,000
Total lease revenue	334,000
Total Lease Payments to be Received [Abstract]
Lease Payments to be Received, Remainder of Fiscal Year	13,659,000
Lease Payments to be Received, Two Years	17,567,000
Lease Payments to be Received, Three Years	17,071,000
Lease Payments to be Received, Four Years	16,602,000
Lease Payments to be Received, Five Years	15,912,000
Lease Payments to be Received, Thereafter	266,657,000
Total lease revenue	$ 347,468,000
Compressed Natural Gas Lease [Member]
Lessor, Lease, Description [Line Items]
Lessor, Sales-type Lease, Term of Contract	10 years
Residual Value of Leased Asset	$ 0
Variable Lease, Payment	0
North Mist Lease [Member]
Lessor, Lease, Description [Line Items]
Residual Value of Leased Asset	0
Variable Lease, Payment	0
Sales-type Lease [Member]
Sales-type Leases Payments to be Received [Abstract]
Sales-type Lease, Payments to be Received, Remainder of Fiscal Year	13,603,000
Sales-type Lease, Payments to be Received, Two Years	17,518,000
Sales-type Lease, Payments to be Received, Three Years	17,026,000
Sales-type Lease, Payments to be Received, Four Years	16,557,000
Sales-type Lease, Payments to be Received, Five Years	15,867,000
Sales-type Lease, Payments to be Received, Thereafter	266,563,000
Total lease revenue	347,134,000
Less: imputed interest	199,041,000
Total leases receivable	$ 148,093,000

Leases - Lease Expense (Details

Leases - Lease Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Lessee, Lease, Description [Line Items]
Residual Value of Leased Asset	$ 4,100		$ 4,000
Lease Expense [Abstract]
Operating Lease, Expense	1,254	$ 1,188
Short-term Lease, Cost	$ 198	160
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	20 years
Northwest Natural Gas Company [Member]
Lease Expense [Abstract]
Operating Lease, Expense	$ 1,202	1,142
Short-term Lease, Cost	198	160
Other Northwest Holdings [Member] | Corporate, Non-Segment [Member]
Lease Expense [Abstract]
Operating Lease, Expense	52	46
Short-term Lease, Cost	$ 0	$ 0

Leases - Lease Asset and Liabil

Leases - Lease Asset and Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Lessee, Lease, Description [Line Items]
Finance Lease, Liability, Payments, Due Next Twelve Months	$ 300
Operating Lease Asset and Liabilities [Abstract]
Operating lease right of use asset	79,522	$ 6,163	$ 2,950
Operating lease liabilities current liabilities	1,071	4,656	2,101
Operating lease liabilities noncurrent liabilities	79,105	1,495	841
Total operating lease liabilities	$ 80,176	$ 6,151	$ 2,942
Operating Lease, Weighted Average Remaining Lease Term	19 years 8 months 12 days	1 year 3 months 18 days	1 year
Operating Lease, Weighted Average Discount Rate, Percent	7.20%	3.79%	3.98%
Maturity of Operating Lease Liabilities [Abstract]
Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year	$ 3,191
Lessee, Operating Lease, Liability, Payments, Due Year Two	6,778
Lessee, Operating Lease, Liability, Payments, Due Year Three	6,866
Lessee, Operating Lease, Liability, Payments, Due Year Four	6,983
Lessee, Operating Lease, Liability, Payments, Due Year Five	7,146
Lessee, Operating Lease, Liability, Payments, Due after Year Five	130,935
Lessee, Operating Lease, Liability, Payments, Due	161,899
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	81,723
Total operating lease liabilities	80,176	$ 6,151	$ 2,942
Operating lease liabilities current liabilities	1,071	4,656	2,101
Operating lease liabilities noncurrent liabilities	79,105	1,495	841
Lease Not Yet Commenced [Abstract]
Lessee, Operating Lease, Liability, Payments, Due	161,899
Leases Cash Flow [Abstract]
Operating cash flows from operating leases	1,248	1,134
Finance Lease, Principal Payments	155	0
Operating leases	77,988	7,291
Finance Leases [Abstract]
Finance Lease, Right-of-Use Asset	700	200	500
Prior Period Disclosures [Abstract]
Right-of-Use Asset Obtained in Exchange for Finance Lease Liability	233	0
Other Northwest Holdings [Member] | Corporate, Non-Segment [Member]
Operating Lease Asset and Liabilities [Abstract]
Operating lease right of use asset	139	260	190
Operating lease liabilities current liabilities	87	179	122
Operating lease liabilities noncurrent liabilities	53	82	69
Total operating lease liabilities	140	261	191
Maturity of Operating Lease Liabilities [Abstract]
Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year	74
Lessee, Operating Lease, Liability, Payments, Due Year Two	52
Lessee, Operating Lease, Liability, Payments, Due Year Three	18
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	144
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	4
Total operating lease liabilities	140	261	191
Operating lease liabilities current liabilities	87	179	122
Operating lease liabilities noncurrent liabilities	53	82	69
Lease Not Yet Commenced [Abstract]
Lessee, Operating Lease, Liability, Payments, Due	144
Leases Cash Flow [Abstract]
Operating cash flows from operating leases	52	43
Operating leases	0	304
Northwest Natural Gas Company [Member]
Operating Lease Asset and Liabilities [Abstract]
Operating lease right of use asset	79,383	5,903	2,760
Operating lease liabilities current liabilities	984	4,477	1,979
Operating lease liabilities noncurrent liabilities	79,052	1,413	772
Total operating lease liabilities	80,036	5,890	2,751
Maturity of Operating Lease Liabilities [Abstract]
Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year	3,117
Lessee, Operating Lease, Liability, Payments, Due Year Two	6,726
Lessee, Operating Lease, Liability, Payments, Due Year Three	6,848
Lessee, Operating Lease, Liability, Payments, Due Year Four	6,983
Lessee, Operating Lease, Liability, Payments, Due Year Five	7,146
Lessee, Operating Lease, Liability, Payments, Due after Year Five	130,935
Lessee, Operating Lease, Liability, Payments, Due	161,755
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	81,719
Total operating lease liabilities	80,036	5,890	2,751
Operating lease liabilities current liabilities	984	4,477	1,979
Operating lease liabilities noncurrent liabilities	79,052	1,413	$ 772
Lease Not Yet Commenced [Abstract]
Lessee, Operating Lease, Liability, Payments, Due	161,755
Leases Cash Flow [Abstract]
Operating cash flows from operating leases	1,196	1,091
Finance Lease, Principal Payments	155	0
Operating leases	77,988	6,987
Prior Period Disclosures [Abstract]
Right-of-Use Asset Obtained in Exchange for Finance Lease Liability	233	$ 0
New Headquarters Lease [Member]
Maturity of Operating Lease Liabilities [Abstract]
Lessee, Operating Lease, Liability, Payments, Due	$ 159,300
Lease Not Yet Commenced [Abstract]
Lessee, Operating Lease, Lease Not yet Commenced, Term of Contract	20 years
Lessee, Operating Lease, Liability, Payments, Due	$ 159,300
New Headquarters Lease Renewal Term 2 of 2 [Member] | New Headquarters Lease [Member]
Lease Not Yet Commenced [Abstract]
Lessee, Operating Lease, Lease Not yet Commenced, Renewal Term	7 years
New Headquarters Lease Renewal Term 1 of 2 [Member] | New Headquarters Lease [Member]
Lease Not Yet Commenced [Abstract]
Lessee, Operating Lease, Lease Not yet Commenced, Renewal Term	7 years

Stock-Based Compensation (Detai

Stock-Based Compensation (Details) - Long Term Incentive Plan $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020USD ($)$ / sharesshares
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares granted (in shares)	39,784
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)	31,076
Weighted-average grant date fair value (in dollars per share) | $ / shares	$ 72.38
Unrecognized compensation costs | $	$ 4,700
Unrecognized Compensation Cost, Period for Recognition	through 2025
A 2019 Award and 2020 Award [Member] | Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Payment Arrangement, Expense | $	$ 0
Target Achieved [Member] | A 2020 Award [Member] | Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share Based Compensation Award Target Share	31,830
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	35,170

Debt Short-term Debt (Details)

Debt Short-term Debt (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Mar. 31, 2019USD ($)
Short-term Debt [Line Items]
Short-term debt	$ 550,000	$ 149,100	$ 176,391
Commercial paper, Maximum remaining maturity	45 days
Commercial paper, Average remaining maturity	25 days
Ratio of Indebtedness to Net Capital	0.625
Northwest Natural Gas Company [Member]
Short-term Debt [Line Items]
Short-term debt	$ 450,000	$ 125,100	$ 176,300
Commercial Paper	$ 73,000
Ratio of Indebtedness to Net Capital	0.614
Line of Credit [Member]
Short-term Debt [Line Items]
Short-term debt	$ 100,000
Line of Credit [Member] | Northwest Natural Gas Company [Member]
Short-term Debt [Line Items]
Short-term debt	$ 227,000
364-Day Term Loan, Due 2021 [Member]
Short-term Debt [Line Items]
Debt Instrument Covenant Consolidated Indebtedness to Capitalization Ratio	70.00%
364-Day Term Loan, Due 2021 [Member] | Northwest Natural Gas Company [Member]
Short-term Debt [Line Items]
Proceeds from Issuance of Debt	$ 150,000

Long-Term Debt (Details)

Long-Term Debt (Details) $ in Thousands	3 Months Ended	6 Months Ended
	Mar. 31, 2020USD ($)	Jun. 30, 2019USD ($)	Dec. 31, 2019USD ($)	Mar. 31, 2019USD ($)
Debt Instrument [Line Items]
Long-term Debt	$ 954,164		$ 881,064	$ 736,642
Unamortized debt issuance costs	$ 7,554		5,712	5,246
Ratio of Indebtedness to Net Capital	0.625
Northwest Natural Gas Company [Member]
Debt Instrument [Line Items]
Long-term Debt	$ 917,146		843,988	734,454
Unamortized debt issuance costs	$ 7,554		$ 5,712	$ 5,246
Weighted average interest rate	4.598%
Ratio of Indebtedness to Net Capital	0.614
Northwest Natural Gas Company [Member] | Minimum [Member]
Debt Instrument [Line Items]
Stated interest rate	2.822%
Northwest Natural Gas Company [Member] | Maximum [Member]
Debt Instrument [Line Items]
Stated interest rate	9.05%
Note 3.60 Series Due 2050 [Member] | Northwest Natural Gas Company [Member]
Debt Instrument [Line Items]
Stated interest rate	3.60%
Proceeds from Issuance of Debt	$ 150,000
Note 537 Series Due 2020 [Member] | Northwest Natural Gas Company [Member]
Debt Instrument [Line Items]
Stated interest rate	5.37%
Repayments of Debt	$ 75,000
Two-year Term Loan Due 2021 [Member]
Debt Instrument [Line Items]
Stated interest rate	1.82%
Proceeds from Issuance of Debt		$ 35,000
Debt Instrument, Covenant Description	requires NW Holdings to maintain a consolidated indebtedness to total capitalization ratio of 70% or less

Debt Fair Value of Long Term De

Debt Fair Value of Long Term Debt (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Debt Instrument [Line Items]
Gross long-term debt		$ 886,776	$ 741,888
Unamortized debt issuance costs	$ (7,554)	(5,712)	(5,246)
Carrying amount	954,164	881,064	736,642
Estimated fair value	1,038,691	957,268	777,778
Northwest Natural Gas Company [Member]
Debt Instrument [Line Items]
Gross long-term debt	924,700	849,700	739,700
Unamortized debt issuance costs	(7,554)	(5,712)	(5,246)
Carrying amount	917,146	843,988	734,454
Estimated fair value	$ 1,001,058	$ 919,835	$ 775,590

Pension and Other Postretirem_3

Pension and Other Postretirement Benefit Costs - Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 1,657	$ 1,517
Interest cost	4,011	4,662
Expected return on plan assets	(5,496)	(5,207)
Amortization of net actuarial loss	0	2
Defined Benefit Plan, Amortization of Gain (Loss)	4,778	3,603
Net periodic benefit cost	4,950	4,577
Amount allocated to construction	(668)	(586)
Defined Benefit Plan Net Periodic Benefit Cost Charged To Expense	4,282	3,991
Regulatory Pension Disallowance	0	10,500
Amortization of Regulatory Balancing Account	2,801	12,511
Net amount charged to expense	7,083	27,002
Other Postretirement Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	64	68
Interest cost	223	281
Expected return on plan assets	0	0
Amortization of net actuarial loss	(117)	(117)
Defined Benefit Plan, Amortization of Gain (Loss)	143	97
Net periodic benefit cost	313	329
Amount allocated to construction	(23)	(24)
Defined Benefit Plan Net Periodic Benefit Cost Charged To Expense	290	305
Regulatory Pension Disallowance	0	0
Amortization of Regulatory Balancing Account	0	0
Net amount charged to expense	$ 290	$ 305

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, 2020	Mar. 31, 2019
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss) [Abstract]
Beginning balance	$ (10,733)	$ (7,188)
Amortization of actuarial losses	218	156
Stranded Deferred Tax Remeasurement Benefit	0	1,366
Total reclassifications before tax	218	(1,210)
Tax (benefit) expense	(58)	(41)
Total reclassifications for the period	160	(1,251)
Ending balance	$ (10,573)	$ (8,439)

Pension and Other Postretirem_5

Pension and Other Postretirement Benefit Costs - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Pension and Other Postretirement Benefits Cost (Reversal of Cost) [Abstract]
Defined benefit pension plan cash contributions	$ 3.2
Estimated future employer contributions in next fiscal year	25
Employer contributions	$ 2.5	$ 2.1

Income Tax (Details)

Income Tax (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2018
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Income taxes at statutory rates (federal and state)	$ 13,105	$ 11,022
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount	3,677	3,291
Differences required to be flowed-through by regulatory commissions	(2,525)	(5,260)
Other, net	(130)	(378)
Total provision for income taxes on continuing operations	$ 14,127	$ 8,675
Effective tax rate for continuing operations	22.80%	16.70%
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)	$ 13,355	$ 11,159
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount	3,737	3,326
Differences required to be flowed-through by regulatory commissions	(2,525)	(5,260)
Other, net	(149)	(377)
Total provision for income taxes on continuing operations	$ 14,418	$ 8,848
Effective tax rate for continuing operations	22.80%	16.80%

Property, Plant and Equipment_3

Property, Plant and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property, plant, and equipment	$ 3,439,460	$ 3,551,065	$ 3,476,746
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	1,005,117	1,050,850	1,037,847
Property, Plant and Equipment, Net	2,434,343	2,500,215	2,438,899
Natural Gas Distribution [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment	3,159,754	3,344,345	3,302,049
Public Utilities, Property, Plant and Equipment, Construction Work in Progress	204,938	95,566	84,965
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	985,961	1,030,234	1,017,931
Property, Plant and Equipment, Net	2,378,731	2,409,677	2,369,083
Other Northwest Natural [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment	65,283	64,314	63,513
Public Utilities, Property, Plant and Equipment, Construction Work in Progress	5,329	4,824	5,548
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	18,851	18,901	18,662
Property, Plant and Equipment, Net	51,761	50,237	50,399
Northwest Natural Gas Company [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Net	2,430,492	2,459,914	2,419,482
Other Northwest Holdings [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment	4,156	42,016	20,671
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	305	1,715	1,254
Property, Plant and Equipment, Net	3,851	40,301	19,417
Northwest Holdings and Northwest Natural [Member]
Property, Plant and Equipment [Line Items]
Property, Plant, Equipment non-cash	25,035	33,999	32,502
Northwest Natural Gas Company [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment	3,435,304	3,509,049	3,456,075
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	1,004,812	1,049,135	1,036,593
Property, Plant and Equipment, Net	2,430,492	$ 2,459,914	$ 2,419,482
Northwest Natural Gas Company [Member] | North Mist Lease [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Transfers and Changes	$ 146,000

Gas Reserves (Details)

Gas Reserves (Details)	3 Months Ended
	Mar. 31, 2020USD ($)
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, 2020	Dec. 31, 2019	Mar. 31, 2019
Reserve Quantities [Line Items]
Gas reserves	$ 14,351	$ 15,278	$ 16,157
Gas reserves, non-current	172,956	172,029	171,150
Less: Accumulated amortization	127,722	123,635	109,243
Total gas reserves	59,585	63,672	78,064
Less: Deferred taxes on gas reserves	14,522	15,515	19,638
Net investment in gas reserves	45,063	48,157	58,426
Jonah Energy LLC
Reserve Quantities [Line Items]
Total Gas Reserves Investment	$ 3,600	$ 3,800	$ 4,500

Investments (Details)

Investments (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
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_3

Business Combinations Business Combinations (Details)	3 Months Ended		12 Months Ended
	Mar. 31, 2020USD ($)	Mar. 31, 2019USD ($)	Dec. 31, 2019USD ($)
Business Acquisition [Line Items]
Goodwill	$ 69,220,000	$ 8,954,000	$ 49,929,000
Goodwill, Impairment Loss	0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets [Abstract]
Goodwill	69,220,000	8,954,000	49,929,000
Suncadia & T&W Water [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred	38,100,000
Goodwill	19,100,000
Business Acquisition, Goodwill, Expected Tax Deductible Amount	17,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill	$ 0
Number of Businesses Acquired	2
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets [Abstract]
Goodwill	$ 19,100,000
Sunriver [Member]
Business Acquisition [Line Items]
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual	$ 1,500,000
Business Combination, Consideration Transferred		$ 55,000,000
Business Acquisition, Connections of Acquired Business		9,400
Goodwill		$ 40,355,000
Business Acquisition, Goodwill, Expected Tax Deductible Amount		50,200,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill		0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets [Abstract]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets		222,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment		13,565,000
Goodwill		40,355,000
Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Assets		828,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities		(22,000)
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets		$ 54,948,000
Other insignificant acquisitions [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred			$ 2,000,000
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, 2020USD ($)therm	Dec. 31, 2019USD ($)therm	Mar. 31, 2019USD ($)therm
Financial [Member] | Gas Year 2019 - 2020 [Member]
Derivative [Line Items]
TargetHedgeAchieved	52.00%
Financial [Member] | Gas Year 2018 - 2019 [Member]
Derivative [Line Items]
TargetHedgeAchieved	48.00%
Physical [Member] | Gas Year 2019 - 2020 [Member]
Derivative [Line Items]
TargetHedgeAchieved	19.00%
Physical [Member] | Gas Year 2018 - 2019 [Member]
Derivative [Line Items]
TargetHedgeAchieved	24.00%
Natural Gas Therms [Member] | Financial [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	487,420	651,540	255,550
Natural Gas Therms [Member] | Physical [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	369,450	512,849	422,825
Foreign Exchange Contract [Member]
Derivative [Line Items]
Derivative, Notional Amount | $	$ 9,885	$ 6,650	$ 7,241

Derivative Instruments Fair Val

Derivative Instruments Fair Value (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Derivative [Line Items]
Derivative, Fair Value, Net	$ (1.3)	$ 7.5	$ 4.4

Unrealized and Realized Gain_Lo

Unrealized and Realized Gain/Loss (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Financial [Member]
Derivative [Line Items]
Derivative, Gain on Derivative		$ 11,300
Derivative, Loss on Derivative	$ (2,100)
Northwest Holdings and Northwest Natural [Member] | Natural gas commodity
Derivative [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	371	(345)
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	5,343	7,007
Northwest Holdings and Northwest Natural [Member] | Benefit (expense) to cost of gas | Foreign exchange
Derivative [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	466	89
Northwest Holdings and Northwest Natural [Member] | Sales [Member] | Natural gas commodity
Derivative [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	2,433	(2,367)
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	(7,405)	9,029
Deferred Derivative Gain (Loss) [Member] | Northwest Holdings and Northwest Natural [Member] | Foreign exchange
Derivative [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	$ (466)	$ (89)

Derivative Instruments Credit R

Derivative Instruments Credit Rating (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Derivative [Line Items]
Additional Collateral, Aggregate Fair Value	$ 2,100,000
Unrealized losses on derivatives	200,000	$ 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	3,000,000	6,400,000	$ 9,400,000
Derivative liability	$ 4,300,000	$ 2,000,000	$ 1,900,000

Environmental Matters (Details)

Environmental Matters (Details)	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Oregon [Member]
Site Contingency [Line Items]
Remediation Recovery Percentage	96.68%	96.68%	96.68%
WASHINGTON
Site Contingency [Line Items]
Remediation Recovery Percentage	3.32%

Environmental Matters - Environ

Environmental Matters - Environmental Sites (Details) $ in Thousands	1 Months Ended		3 Months Ended
	Jan. 31, 2017USD ($)	May 31, 2012USD ($)	Mar. 31, 2020USD ($)propertyparty	Dec. 31, 2019USD ($)	Mar. 31, 2019USD ($)
Site Contingency [Line Items]
Current Liabilities			$ 37,909	$ 39,225	$ 30,143
Non-Current Liabilities			92,423	96,797	94,364
Gasco/Siltronic Sediments
Site Contingency [Line Items]
Current Liabilities			11,829	11,632	4,595
Non-Current Liabilities			42,837	46,082	44,427
Site Contingency, Environmental Remediation Costs Recognized			54,700
Gasco/Siltronic Sediments | Minimum [Member]
Site Contingency [Line Items]
Environmental Exit Costs, Anticipated Cost		$ 54,700
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			2,554	2,543	2,299
Non-Current Liabilities			$ 6,574	6,920	5,958
Gasco Uplands [Member]
Site Contingency [Line Items]
Site contingency: number of management pieces			2
Gasco/Siltronic Upland [Member]
Site Contingency [Line Items]
Current Liabilities			$ 12,822	14,203	11,951
Non-Current Liabilities			42,833	43,616	43,800
Central Service Center [Member]
Site Contingency [Line Items]
Current Liabilities			0	0	10
Non-Current Liabilities			$ 0	0	0
Environmental monitoring activities, duration			5 years
Front Street [Member]
Site Contingency [Line Items]
Current Liabilities			$ 10,704	10,847	11,288
Non-Current Liabilities			0	0	0
Undiscounted environmental remediation expense			9,800
Additional studies and design costs			900
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, 2020	Dec. 31, 2019	Mar. 31, 2019
Site Contingency [Line Items]
Regulatory Assets, Current	$ 37,815	$ 41,929	$ 46,317
Regulatory Assets, Noncurrent	$ 328,024	$ 343,146	$ 327,194
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
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	37,815	41,929	46,317
Regulatory Assets, Noncurrent	328,024	343,146	327,194
Northwest Natural Gas Company [Member] | Environmental costs [Member]
Site Contingency [Line Items]
Deferred costs and interest	37,586	36,673	36,874
Accrued site liabilities	129,977	135,662	124,133
Insurance proceeds and interest	(80,613)	(79,949)	(89,305)
Regulatory Assets	86,950	92,386	71,702
Regulatory Assets, Current	4,459	4,762	5,090
Regulatory Assets, Noncurrent	$ 82,491	$ 87,624	$ 66,612

Discontinued Operations (Detail

Discontinued Operations (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Jun. 30, 2020	Dec. 31, 2019
Disposal Group, Including Discontinued Operation, Classified Balance Sheet Disclosures [Abstract]
Discontinued operations - total assets	$ 15,300	$ 14,600		$ 15,100
Discontinued Operation, Income Statement Disclosures [Abstract]
Loss from discontinued operations, net of tax	$ (778)	$ (217)
Loss from discontinued operations per share of common stock
Basic (in dollars per share)	$ (0.02)	$ (0.01)
Diluted (in dollars per share)	$ (0.02)	$ (0.01)
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	$ 514	$ 1,277		333
Inventories	689	627		695
Other current assets	386	337		457
Property, plant, and equipment	13,349	12,033		13,291
Less: Accumulated depreciation	7	7		7
Operating lease right of use asset	118	118		118
Other non-current assets	247	247		247
Discontinued operations - total assets	15,296	14,632		15,134
Accounts payable	717	1,102		1,250
Other current liabilities	553	359		848
Operating lease liabilities	110	111		116
Other non-current liabilities	11,421	11,710		11,495
Total discontinued operations liabilities	12,801	13,282		$ 13,709
Gill Ranch [Member] | Discontinued Operations, Held-for-sale [Member]
Discontinued Operation, Income Statement Disclosures [Abstract]
Revenues	908	1,721
Operations and maintenance	1,580	1,613
General taxes	47	59
Depreciation and amortization	106	106
Other expenses and interest	231	237
Total expenses	1,964	2,015
Loss from discontinued operations before income tax	(1,056)	(294)
Income tax benefit	(278)	(77)
Loss from discontinued operations, net of tax	$ (778)	$ (217)
Loss from discontinued operations per share of common stock
Basic (in dollars per share)	$ (0.02)	$ (0.01)
Diluted (in dollars per share)	$ (0.02)	$ (0.01)
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%
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
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