Northwest Natural Holding 10-Q 6 Aug 19 2019 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2019	Jul. 26, 2019
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Jun. 30, 2019
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	220 N.W. Second Avenue
Entity Address, City or Town	Portland
Entity Address, State or Province	OR
Entity Address, Postal Zip Code	97209
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		30,442,700
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
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	Jun. 30, 2019
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	220 N.W. Second Avenue
Entity Address, City or Town	Portland
Entity Address, State or Province	OR
Entity Address, Postal Zip Code	97209
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	2019
Document Fiscal Period Focus	Q2
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		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Operating revenues [Abstract]
Operating revenues	$ 123,443	$ 124,567	$ 408,791	$ 388,202
Operating expenses:
Cost of gas	35,107	42,053	140,564	150,159
Operations and maintenance	39,486	38,028	90,968	77,551
Environmental remediation	(2,656)	1,882	6,291	6,506
General taxes	7,879	7,729	16,906	17,203
Revenue taxes	4,496	4,780	16,422	17,209
Depreciation and amortization	22,387	21,147	43,959	42,022
Other operating expenses	646	679	1,538	1,532
Total operating expenses	107,345	116,298	316,648	312,182
Income from operations	16,098	8,269	92,143	76,020
Other income (expense), net	(2,768)	7	(16,515)	(827)
Interest expense, net	10,654	8,771	20,859	18,045
Income before income taxes	2,676	(495)	54,769	57,148
Income tax expense	625	(156)	9,300	15,476
Net income from continuing operations	2,051	(339)	45,469	41,672
Loss from discontinued operations, net of tax	(956)	(659)	(1,173)	(1,133)
Net income (loss)	1,095	(998)	44,296	40,539
Other comprehensive income:
Amortization of non-qualified employee benefit plan liability, net of taxes	115	153	230	307
Comprehensive income (loss)	$ 1,210	$ (845)	$ 44,526	$ 40,846
Average common shares outstanding:
Basic (in shares)	29,337	28,791	29,123	28,772
Diluted (in shares)	29,394	28,791	29,186	28,825
Earnings from continuing operations per share of common stock:
Basic (in dollars per share)	$ 0.07	$ (0.01)	$ 1.56	$ 1.45
Diluted (in dollars per share)	0.07	(0.01)	1.56	1.45
Earnings (loss) per share of common stock:
Basic (in dollars per share)	0.04	(0.03)	1.52	1.41
Diluted (in dollars per share)	$ 0.04	$ (0.03)	$ 1.52	$ 1.41
Northwest Natural Gas Company [Member]
Operating revenues [Abstract]
Operating revenues	$ 122,242	$ 124,563	$ 407,088	$ 388,198
Operating expenses:
Cost of gas	35,163	42,107	140,676	150,271
Operations and maintenance	37,292	37,899	87,726	77,399
Environmental remediation	(2,656)	1,882	6,291	6,506
General taxes	7,826	7,721	16,814	17,180
Revenue taxes	4,496	4,780	16,422	17,209
Depreciation and amortization	22,243	21,090	43,747	41,958
Other operating expenses	638	679	1,528	1,532
Total operating expenses	105,002	116,158	313,204	312,055
Income from operations	17,240	8,405	93,884	76,143
Other income (expense), net	(2,814)	(33)	(16,582)	(848)
Interest expense, net	10,387	8,771	20,520	18,045
Income before income taxes	4,039	(399)	56,782	57,250
Income tax expense	985	(128)	9,833	15,507
Net income from continuing operations	3,054	(271)	46,949	41,743
Loss from discontinued operations, net of tax	0	(727)	0	(1,204)
Net income (loss)	3,054	(998)	46,949	40,539
Other comprehensive income:
Amortization of non-qualified employee benefit plan liability, net of taxes	115	153	230	307
Comprehensive income (loss)	$ 3,169	$ (845)	$ 47,179	$ 40,846

Consolidated Statements of Co_2

Consolidated Statements of Comprehensive Income (Parentheticals) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Amortization of non-qualified employee benefit plan liability, tax	$ 41	$ 56	$ 82	$ 111
Northwest Natural Gas Company [Member]
Amortization of non-qualified employee benefit plan liability, tax	$ 41	$ 56	$ 82	$ 111

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Current assets:
Cash and cash equivalents	$ 60,885	$ 12,633	$ 8,755
Accounts receivable	42,670	66,970	31,512
Accrued unbilled revenue	14,840	57,827	13,995
Allowance for uncollectible accounts	(814)	(977)	(657)
Regulatory assets	46,688	41,930	41,092
Derivative instruments	2,186	9,001	2,044
Inventories	23,100	44,149	43,109
Gas reserves	17,206	16,647	16,579
Income Taxes Receivable, Current	0	6,000	0
Other current assets	18,296	28,472	11,672
Discontinued operations - current assets	14,001	13,269	12,743
Total current assets	239,058	295,921	180,844
Non-current assets:
Property, plant, and equipment	3,355,811	3,414,490	3,298,856
Less: Accumulated depreciation	1,016,185	993,118	984,998
Property, Plant and Equipment, Net	2,339,626	2,421,372	2,313,858
Gas reserves	56,171	66,197	75,362
Regulatory assets	318,340	371,786	339,177
Derivative instruments	670	725	1,077
Other investments	62,815	63,558	64,854
Operating lease right of use asset	5,013	0	0
Assets under sales-type leases	148,886	0	0
Goodwill	49,393	8,954	0
Other non-current assets	18,159	14,149	11,588
Total non-current assets	2,999,073	2,946,741	2,805,916
Total assets	3,238,131	3,242,662	2,986,760
Current liabilities:
Short-term debt	20,080	217,620	47,100
Current maturities of long-term debt	104,396	29,989	74,785
Accounts payable	76,429	115,878	70,551
Taxes accrued	7,003	11,023	6,916
Interest accrued	7,826	7,306	6,652
Regulatory liabilities	32,484	47,436	34,275
Derivative instruments	4,650	12,381	11,744
Operating lease liabilities	4,271	0	0
Other current liabilities	36,612	54,492	32,935
Discontinued operations current liabilities	13,279	12,959	12,922
Total current liabilities	307,030	509,084	297,880
Long-term debt	806,001	706,247	683,895
Deferred credits and other non-current liabilities:
Deferred tax liabilities	292,791	280,463	281,028
Regulatory liabilities	605,036	611,560	602,294
Pension and other postretirement benefit liabilities	217,909	221,886	218,061
Derivative instruments	2,062	3,025	3,913
Operating lease liabilities	721	0	0
Other non-current liabilities	129,835	147,763	140,163
Discontinued operations non-current liabilities			12,700
Total deferred credits and other non-current liabilities	1,248,354	1,264,697	1,245,459
Commitments and contingencies (see Note 16 and Note 17)
Equity:
Common stock	555,052	457,640	452,195
Retained earnings	330,018	312,182	315,462
Accumulated other comprehensive loss	(8,324)	(7,188)	(8,131)
Total equity	876,746	762,634	759,526
Total liabilities and equity	3,238,131	3,242,662	2,986,760
Northwest Natural Gas Company [Member]
Current assets:
Cash and cash equivalents	57,864	7,947	8,322
Accounts receivable	42,180	66,824	31,512
Accrued unbilled revenue	14,730	57,773	13,995
Receivables from affiliates	289	4,166	265
Allowance for uncollectible accounts	(812)	(975)	(657)
Regulatory assets	46,688	41,930	41,092
Derivative instruments	2,186	9,001	2,044
Inventories	22,999	44,126	43,109
Gas reserves	17,206	16,647	16,579
Other current assets	18,259	25,347	11,603
Discontinued operations - current assets	0	0	5,873
Total current assets	221,589	272,786	173,737
Non-current assets:
Property, plant, and equipment	3,337,005	3,410,439	3,298,481
Less: Accumulated depreciation	1,015,761	992,855	984,791
Property, Plant and Equipment, Net	2,321,244	2,417,584	2,313,690
Gas reserves	56,171	66,197	75,362
Regulatory assets	318,340	371,786	339,177
Derivative instruments	670	725	1,077
Other investments	49,281	49,922	51,181
Operating lease right of use asset	4,797	0	0
Assets under sales-type leases	148,886	0	0
Other non-current assets	17,715	13,736	11,578
Discontinued operations - non-current assets	0	0	25,037
Total non-current assets	2,917,104	2,919,950	2,817,102
Total assets	3,138,693	3,192,736	2,990,839
Current liabilities:
Short-term debt	0	217,500	47,100
Current maturities of long-term debt	104,359	29,989	74,785
Accounts payable	74,918	114,937	70,155
Payables to affiliates	6,878	523	3,811
Taxes accrued	6,903	10,990	6,887
Interest accrued	7,675	7,273	6,652
Regulatory liabilities	32,484	47,436	34,275
Derivative instruments	4,650	12,381	11,744
Operating lease liabilities	4,141	0	0
Other current liabilities	35,113	53,027	31,934
Discontinued operations current liabilities	0	0	2,702
Total current liabilities	277,121	494,056	290,045
Long-term debt	768,947	704,134	683,895
Deferred credits and other non-current liabilities:
Deferred tax liabilities	307,133	294,739	296,050
Regulatory liabilities	605,036	611,560	602,294
Pension and other postretirement benefit liabilities	217,909	221,886	218,061
Derivative instruments	2,062	3,025	3,913
Operating lease liabilities	634	0	0
Other non-current liabilities	129,736	147,668	140,073
Discontinued operations non-current liabilities	0	0	3,018
Total deferred credits and other non-current liabilities	1,262,510	1,278,878	1,257,373
Equity:
Common stock	319,634	226,452	452,195
Retained earnings	518,805	496,404	315,462
Accumulated other comprehensive loss	(8,324)	(7,188)	(8,131)
Total equity	830,115	715,668	759,526
Total liabilities and equity	$ 3,138,693	$ 3,192,736	$ 2,990,839

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parentheticals) - $ / shares shares in Thousands, $ / shares in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Statement of Financial Position [Abstract]
Shares outstanding (in shares)	30,422	28,880	28,800
Shares Authorized (in shares)	100,000	100,000	100,000
Shares issued (in shares)	30,422	28,880	28,800
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, 2017	$ 742,776	$ 448,865	$ 302,349	$ (8,438)	$ 742,776	$ 448,865	$ 302,349	$ (8,438)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	40,539		40,539		40,539		40,539
Dividends on common stock			(27,426)				(27,426)
Stranded Deferred Tax Remeasurement Benefit	0
Stranded Deferred Tax Remeasurement Benefit | Accounting Standards Update 2018-02 [Member]			0	0			0	0
Other comprehensive income	40,846			307	40,846			307
Stock-based compensation		1,924				1,924
Shares issued pursuant to equity based plans		1,406				1,406
Capital contribution from parent					0	0
Stock Issued During Period, Value, New Issues		0
Ending Balance at Jun. 30, 2018	$ 759,526	452,195	315,462	(8,131)	759,526	452,195	315,462	(8,131)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends per share of common stock	$ 0.9450
Beginning Balance at Mar. 31, 2018	$ 772,205	450,408	330,081	(8,284)	772,205	450,408	330,081	(8,284)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	(998)		(998)		(998)		(998)
Dividends on common stock			(13,621)				(13,621)
Stranded Deferred Tax Remeasurement Benefit	0
Stranded Deferred Tax Remeasurement Benefit | Accounting Standards Update 2018-02 [Member]			0	0			0	0
Other comprehensive income	(845)			153	(845)			153
Stock-based compensation		752				752
Shares issued pursuant to equity based plans		1,035				1,035
Capital contribution from parent						0
Stock Issued During Period, Value, New Issues		0
Ending Balance at Jun. 30, 2018	$ 759,526	452,195	315,462	(8,131)	759,526	452,195	315,462	(8,131)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends per share of common stock	$ 0.4725
Beginning Balance at Dec. 31, 2018	$ 762,634	457,640	312,182	(7,188)	715,668	226,452	496,404	(7,188)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	44,296		44,296		46,949		46,949
Dividends on common stock			(27,826)				(25,914)
Stranded Deferred Tax Remeasurement Benefit	1,366
Stranded Deferred Tax Remeasurement Benefit | Accounting Standards Update 2018-02 [Member]	1,400		1,366	(1,366)			1,366	(1,366)
Other comprehensive income	44,526			230	47,179			230
Stock-based compensation		1,824				0
Shares issued pursuant to equity based plans		2,636				0
Capital contribution from parent					93,182	93,182
Stock Issued During Period, Value, New Issues	92,800	92,952
Ending Balance at Jun. 30, 2019	$ 876,746	555,052	330,018	(8,324)	830,115	319,634	518,805	(8,324)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends per share of common stock	$ 0.9500
Beginning 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]
Net income	1,095		1,095		3,054		3,054
Dividends on common stock			(13,811)				(12,979)
Stranded Deferred Tax Remeasurement Benefit	0
Stranded Deferred Tax Remeasurement Benefit | Accounting Standards Update 2018-02 [Member]			0	0			0	0
Other comprehensive income	1,210			115	3,169			115
Stock-based compensation		579				0
Shares issued pursuant to equity based plans		1,589				0
Capital contribution from parent						93,182
Stock Issued During Period, Value, New Issues		92,952
Ending Balance at Jun. 30, 2019	$ 876,746	$ 555,052	$ 330,018	$ (8,324)	$ 830,115	$ 319,634	$ 518,805	$ (8,324)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends per share of common stock	$ 0.4750

Consolidated Statement of Cash

Consolidated Statement of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Operating activities:
Net income	$ 44,296	$ 40,539
Adjustments to reconcile net income to cash provided by operations:
Depreciation and amortization	43,959	42,022
Regulatory amortization of gas reserves	9,467	7,816
Deferred income taxes	5,917	11,227
Qualified defined benefit pension plan expense	6,988	2,876
Contributions to qualified defined benefit pension plans	(4,650)	(5,570)
Deferred environmental expenditures, net	(7,148)	(7,330)
Amortization of environmental remediation	6,291	6,506
Regulatory revenue recovery deferral from the TCJA	639	9,212
Regulatory disallowance of pension costs	10,500	0
Other	6,282	810
Changes in assets and liabilities:
Receivables, net	69,036	79,332
Inventories	14,929	4,803
Income and other taxes	16,300	(11,967)
Accounts payable	(27,843)	(26,613)
Interest accrued	520	(121)
Deferred gas costs	(44,850)	4,787
Decoupling mechanism	8,635	4,613
Other, net	(4,797)	(990)
Discontinued operations	638	700
Cash provided by operating activities	155,109	162,652
Investing activities:
Capital expenditures	(91,147)	(102,370)
Acquisitions, net of cash acquired	(55,811)	0
Other	(5,389)	195
Discontinued operations	(1,050)	(283)
Cash used in investing activities	(153,397)	(102,458)
Financing activities:
Proceeds from stock options exercised	1,723	45
Proceeds from common stock issued	93,182	0
Long-term debt issued	175,000	0
Long-term debt retired	0	(22,000)
Change in short-term debt	(197,540)	(7,100)
Cash dividend payments on common stock	(25,916)	(25,577)
Other	91	(279)
Net Cash Provided by (Used in) Financing Activities	46,540	(54,911)
Increase in cash and cash equivalents	48,252	5,283
Cash and cash equivalents, beginning of period	12,633	3,472
Cash and cash equivalents, end of period	60,885	8,755
Supplemental disclosure of cash flow information:
Interest paid, net of capitalization	19,725	17,117
Income taxes paid (refunded), net	(6,095)	13,347
Northwest Natural Gas Company [Member]
Operating activities:
Net income	46,949	40,539
Adjustments to reconcile net income to cash provided by operations:
Depreciation and amortization	43,747	41,958
Regulatory amortization of gas reserves	9,467	7,816
Deferred income taxes	5,042	9,387
Qualified defined benefit pension plan expense	6,988	2,876
Contributions to qualified defined benefit pension plans	(4,650)	(5,570)
Deferred environmental expenditures, net	(7,148)	(7,330)
Amortization of environmental remediation	6,291	6,506
Regulatory revenue recovery deferral from the TCJA	639	9,212
Regulatory disallowance of pension costs	10,500	0
Other	5,563	1,180
Changes in assets and liabilities:
Receivables, net	73,186	79,333
Inventories	14,923	4,434
Income and other taxes	7,199	(11,957)
Accounts payable	(23,744)	(26,195)
Interest accrued	402	(121)
Deferred gas costs	(44,850)	4,787
Decoupling mechanism	8,635	4,613
Other, net	(3,003)	(1,990)
Discontinued operations	0	3,104
Cash provided by operating activities	156,136	162,582
Investing activities:
Capital expenditures	(90,675)	(102,370)
Other	(5,389)	195
Discontinued operations	0	(284)
Cash used in investing activities	(96,064)	(102,459)
Financing activities:
Capital contribution from parent	93,182	0
Long-term debt issued	140,000	0
Long-term debt retired	0	(22,000)
Change in short-term debt	(217,500)	(7,100)
Cash dividend payments on common stock	(25,914)	(25,577)
Other	77	(234)
Net Cash Provided by (Used in) Financing Activities	(10,155)	(54,911)
Increase in cash and cash equivalents	49,917	5,212
Cash and cash equivalents, beginning of period	7,947	3,110
Cash and cash equivalents, end of period	57,864	8,322
Supplemental disclosure of cash flow information:
Interest paid, net of capitalization	19,529	17,117
Income taxes paid (refunded), net	$ (6,095)	$ 13,347

Organization and Principles of

Organization and Principles of Consolidation	6 Months Ended
	Jun. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Principles of Consolidation	ORGANIZATION AND PRINCIPLES OF CONSOLIDATION On October 1, 2018, we completed a reorganization into a holding company structure. In this reorganization, shareholders of NW Natural (the predecessor publicly held parent company) became shareholders of NW Holdings on a one-for-one basis; maintaining the same number of shares and ownership percentage as held in NW Natural immediately prior to the reorganization. NW Natural became a wholly-owned subsidiary of NW Holdings. Additionally, certain subsidiaries of NW Natural were transferred to NW Holdings. This reorganization was accounted for as a transaction among entities under common control. As required under accounting guidance, these subsidiaries are presented in this report as discontinued operations in the consolidated results of NW Natural. See Note 18 for additional information. The accompanying consolidated financial statements represent the respective, consolidated financial results of NW Holdings and NW Natural and all respective companies that each registrant directly or indirectly controls, either through majority ownership or otherwise. This is a combined report of NW Holdings and NW Natural, which includes separate consolidated financial statements for each registrant. NW Natural's regulated natural gas distribution activities are reported in the natural gas distribution (NGD) segment. The NGD segment is NW Natural's core operating business and serves residential, commercial, and industrial customers in Oregon and southwest Washington. The NGD segment is the only reportable segment for NW Holdings and NW Natural. All other activities, water businesses, and other investments are aggregated and reported as other at their respective registrant. In addition, NW Holdings has reported discontinued operations results related to the pending sale of Gill Ranch Storage, LLC (Gill Ranch). All prior period amounts have been retrospectively adjusted to reflect this change both in operational results and reportable segments for NW Holdings and NW Natural, respectively. These reclassifications and the reorganization activities described above had no effect on the prior year’s consolidated results of operations, financial condition, or cash flows. See Note 18 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 Environmental, LLC; ▪ NW Natural Water of Washington, LLC (NWN Water of Washington); • Cascadia Infrastructure, LLC; ▪ Cascadia Water, LLC (Cascadia); ▪ NW Natural Water of Idaho, LLC (NWN Water of Idaho); • Gem State Water Company, LLC (Gem State); and • Gem State Infrastructure, LLC. Investments in corporate joint ventures and partnerships that NW Holdings does not directly or indirectly control, and for which it is not the primary beneficiary, include NNG Financial's investment in Kelso-Beaver Pipeline and NWN Energy's investment in Trail West Holdings, LLC (TWH), which are accounted for under the equity method. NW Holdings and its direct and indirect subsidiaries are collectively referred to herein as NW Holdings, and NW Natural and its direct and indirect subsidiaries are collectively referred to herein as NW Natural. The consolidated financial statements of NW Holdings and NW Natural are presented after elimination of all intercompany balances and transactions. Information presented in these interim consolidated financial statements is unaudited, but includes all material adjustments management considers necessary for a fair statement of the results for each period reported including normal recurring accruals. These consolidated financial statements should be read in conjunction with the audited consolidated financial statements and related notes included in NW Holdings' and NW Natural's combined 2018 Annual Report on Form 10-K ( 2018 Form 10-K). A significant part of NW 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 and for NW Natural up until the holding company reorganization was effective on October 1, 2018 on the consolidated statements of comprehensive income and cash flows, and the assets and liabilities associated with Gill Ranch have been classified as discontinued operations assets and liabilities on the NW Holdings consolidated balance sheet. See Note 18 for additional information. Additionally, we reevaluated reportable segments and concluded that the remaining gas storage activities no longer meet the requirements to be separately reported as a segment. Interstate Storage Services is now reported in Other under NW Natural and NW Holdings as applicable, and all prior periods reflect this change. See Note 4 , which provides segment information.

Significant Accounting Policies

Significant Accounting Policies	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Significant Accounting Policies	SIGNIFICANT ACCOUNTING POLICIES Significant accounting policies are described in Note 2 of the 2018 Form 10-K. There were no material changes to those accounting policies during the six months ended June 30, 2019 other than those set forth in this Note 2 . The following are current updates to certain critical accounting policy estimates and new accounting standards. Industry Regulation In applying regulatory accounting principles, NW Holdings and NW Natural capitalize or defer certain costs and revenues as regulatory assets and liabilities pursuant to orders of the Oregon Public Utilities Commission (OPUC), Washington Utilities and Transportation Commission (WUTC) or Idaho Public Utilities Commission (IPUC), which provide for the recovery of revenues or expenses from, or refunds to, utility customers in future periods, including a return or a carrying charge in certain cases. Amounts deferred as regulatory assets and liabilities were as follows: Regulatory Assets June 30, December 31, In thousands 2019 2018 2018 Current: Unrealized loss on derivatives (1) $ 4,385 $ 11,744 $ 12,381 Gas costs 19,195 273 2,873 Environmental costs (2) 5,089 5,594 5,601 Decoupling (3) 1,680 10,232 9,140 Pension balancing (4) 5,009 — — Income taxes 2,209 2,217 2,218 Other (5) 9,121 11,032 9,717 Total current $ 46,688 $ 41,092 $ 41,930 Non-current: Unrealized loss on derivatives (1) $ 2,062 $ 3,913 $ 3,025 Pension balancing (4) 50,080 67,527 74,173 Income taxes 17,758 19,267 19,185 Pension and other postretirement benefit liabilities 168,137 171,186 174,993 Environmental costs (2) 68,240 65,156 76,149 Gas costs 2,994 28 9,978 Decoupling (3) 37 1,636 2,545 Other (5) 9,032 10,464 11,738 Total non-current $ 318,340 $ 339,177 $ 371,786 Regulatory Liabilities June 30, December 31, In thousands 2019 2018 2018 Current: Gas costs $ 5,630 $ 20,906 $ 17,182 Unrealized gain on derivatives (1) 1,944 1,938 8,740 Decoupling (3) 857 2,153 2,264 Income taxes 7,763 — — Other (5) 16,290 9,278 19,250 Total current $ 32,484 $ 34,275 $ 47,436 Non-current: Gas costs $ 226 $ 3,460 $ 552 Unrealized gain on derivatives (1) 670 1,077 725 Decoupling (3) 74 410 — Income taxes (6) 202,422 222,734 225,408 Accrued asset removal costs (7) 390,345 370,245 380,464 Other (5) 11,299 4,368 4,411 Total non-current $ 605,036 $ 602,294 $ 611,560 (1) Unrealized gains or losses on derivatives are non-cash items and therefore do not earn a rate of return or a carrying charge. These amounts are recoverable through NGD rates as part of the annual Purchased Gas Adjustment (PGA) mechanism when realized at settlement. (2) Refer to footnote (3) of the Deferred Regulatory Asset table in Note 17 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 10 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 11 . (7) Estimated costs of removal on certain regulated properties are collected through rates. We believe all costs incurred and deferred at June 30, 2019 are prudent. All regulatory assets and liabilities are reviewed annually for recoverability, or more often if circumstances warrant. If we should determine that all or a portion of these regulatory assets or liabilities no longer meet the criteria for continued application of regulatory accounting, then NW Natural would be required to write-off the net unrecoverable balances in the period such determination is made. New Accounting Standards We consider the applicability and impact of all accounting standards updates (ASUs) issued by the Financial Accounting Standards Board (FASB). ASUs not listed below were assessed and determined to be either not applicable or are expected to have minimal impact on NW Natural's consolidated financial position or results of operations. Recently Adopted Accounting Pronouncements ACCUMULATED OTHER COMPREHENSIVE INCOME. On February 14, 2018, the FASB issued ASU 2018-02, "Income Statement—Reporting Comprehensive Income: Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income." This update was issued in response to concerns from certain stakeholders regarding the current requirements under U.S. GAAP that deferred tax assets and liabilities are adjusted for a change in tax laws or rates, and the effect is to be included in income from continuing operations in the period of the enactment date. This requirement is also applicable to items in accumulated other comprehensive income where the related tax effects were originally recognized in other comprehensive income. The adjustment of deferred taxes due to the new corporate income tax rate enacted through the Tax Cuts and Jobs Act (TCJA) on December 22, 2017 recognized in income from continuing operations causes the tax effects of items within accumulated other comprehensive income (referred to as stranded tax effects) to not reflect the appropriate tax rate. The amendments in this update allow but do not require a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the TCJA and require certain disclosures about stranded tax effects. NW Natural adopted and applied the standard in the first quarter of 2019. NW Natural elected to reclassify the stranded tax effects of the TJCA of $1.4 million from accumulated other comprehensive loss to retained earnings in the period of adoption. Going forward, our policy is that, in the event that regulation changes result in stranded tax effects, such amounts will be reclassified from accumulated other comprehensive income (loss) to retained earnings in the final period that the related deferred tax balance remeasurement is expected to impact income from continuing operations. DERIVATIVES AND HEDGING. On August 28, 2017, the FASB issued ASU 2017-12, "Derivatives and Hedging: Targeted Improvements to Accounting for Hedging Activities." The purpose of the amendment is to more closely align hedge accounting with companies’ risk management strategies. The ASU amends the accounting for risk component hedging, the hedged item in fair value hedges of interest rate risk, and amounts excluded from the assessment of hedge effectiveness. The guidance also amends the recognition and presentation of the effect of hedging instruments and includes other simplifications of hedge accounting. The amendments in this update were effective beginning January 1, 2019 and were applied prospectively to hedging instruments. The adoption did not have an impact on the financial statements or disclosures of NW Holdings or NW Natural. GOODWILL. On January 26, 2017, the FASB issued ASU 2017-04, "Simplifying the Test for Goodwill Impairment." The ASU removes Step 2 from the goodwill impairment test and under the amended guidance an entity should perform its annual goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount and recognize an impairment charge for the amount in which the carrying amounts exceed the fair value of the reporting unit. The amendments in this standard are effective for us beginning January 1, 2020 and early adoption is permitted for interim or annual goodwill impairment tests performed after January 1, 2017. NW Natural early adopted ASU 2017-04 in the quarter ended September 30, 2018. The adoption of this ASU did not materially affect the financial statements and disclosures of NW Holdings or NW Natural. LEASES. On February 25, 2016, the FASB issued ASU 2016-02, "Leases," which revises the existing lease accounting guidance. Pursuant to the new standard (“ASC 842”), lessees are required to recognize all leases, including operating leases that are greater than 12 months at lease commencement, on the balance sheet and record corresponding right of use assets and lease liabilities. Lessor accounting will remain substantially the same under the new standard. Quantitative and qualitative disclosures are also required for users of the financial statements to have a clear understanding of the nature of our leasing activities. We elected the alternative prospective transition approach for adoption beginning January 1, 2019. All comparative periods prior to January 1, 2019 will retain the financial reporting and disclosure requirements of ASC 840 “Leases” (“ASC 840”). There was no cumulative effect adjustment to the opening balance of retained earnings recorded as of January 1, 2019 for adoption as there were no initial direct costs or other capitalized costs related to the legacy leases that needed to be derecognized upon adoption of ASC 842. We elected the land easement optional practical expedient to not evaluate existing or expired land easements that were not previously accounted for as leases under the ASC 840 lease guidance. For the existing lease portfolio, we did not elect the optional practical expedient package to retain the legacy lease accounting conclusions upon adoption; we re-assessed our existing contracts under the new leasing standard including whether the contract meets the definition of a lease and lease classification. As a result, we determined that most of our underground gas storage contracts no longer meet the definition of a lease under the new lease standard. Our lease portfolio under the new standard consists primarily of our current leased headquarters, which expires in 2020. In October 2017, NW Natural entered into a 20-year operating lease agreement commencing in 2020 for a new headquarters location in Portland, Oregon. The lease was analyzed under ASC 840 in consideration of build-to-suit lease accounting guidance with the conclusion that NW Natural was the owner of the asset during construction for accounting purposes. Under the new lease standard, ASC 842, NW Natural is no longer considered the owner of the asset during construction for accounting purposes. As such, in January 2019 we derecognized the build-to-suit asset and liability balances of $26.0 million as of December 31, 2018 that were previously recorded within property, plant and equipment and other non-current liabilities in the consolidated balance sheet. Upon adoption on January 1, 2019, NW Holdings recorded an operating lease right of use asset and an associated operating lease liability of approximately $7.3 million , of which $7.0 million was recorded at NW Natural. Lease liabilities are measured using NW Natural's incremental borrowing rate based on information available at the lease commencement date in determining the present value of lease payments. See Note 7 . CLOUD COMPUTING. On August 29, 2018, the FASB issued ASU 2018-15, "Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract." The purpose of the amendment is to align the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. The amendments in this update are effective for us beginning January 1, 2020. Early adoption is permitted, and NW Holdings and NW Natural early adopted ASU 2018-15 in the quarter ended March 31, 2019 utilizing the prospective application methodology. The adoption of this ASU did not materially affect the financial statements and disclosures of NW Holdings or NW Natural. Recently Issued Accounting Pronouncements RETIREMENT BENEFITS. On August 28, 2018, the FASB issued ASU 2018-14, "Changes to the Disclosure Requirements for Defined Benefit Plans." The purpose of the amendment is to modify the disclosure requirements for defined benefit pension and other postretirement plans. The amendments in this update are effective for us beginning January 1, 2020. Early adoption is permitted. The amended presentation and disclosure guidance should be applied retrospectively. We are currently assessing the effect of this standard on disclosures. FAIR VALUE MEASUREMENT. On August 28, 2018, the FASB issued ASU 2018-13, "Changes to the Disclosure Requirements for Fair Value Measurement." The purpose of the amendment is to modify the disclosure requirements for fair value measurements. The amendments in this update are effective for us beginning January 1, 2020. Early adoption is permitted. The amendments on changes in unrealized gains and losses, the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements and the narrative description of measurement uncertainty should be applied prospectively. All other amendments should be applied retrospectively. We are currently assessing the effect of this standard on disclosures. CREDIT LOSSES. On June 16, 2016, the FASB issued ASU 2016-13, "Measurement of Credit Losses on Financial Instruments," which applies to financial assets subject to credit losses and measured at amortized cost. The new standard will require financial assets measured at amortized cost to be presented at the net amount expected to be collected and the allowance for credit losses is to be recorded as a valuation account that is deducted from the amortized cost basis. The amendments in this update are effective beginning January 1, 2020. Early adoption is permitted for fiscal years beginning after December 15, 2018. We are currently assessing the effect of this standard, and subsequent standard updates which clarify ASU 2016-13, on our financial statements and disclosures.

Earnings Per Share

Earnings Per Share	6 Months Ended
	Jun. 30, 2019
Earnings Per Share [Abstract]
Earnings Per Share	EARNINGS PER SHARE Basic earnings per share are computed using NW Holdings' net income and the weighted average number of common shares outstanding for each period presented. Diluted earnings per share are computed in the same manner, except using the weighted average number of common shares outstanding plus the effects of the assumed exercise of stock options and the payment of estimated stock awards from other stock-based compensation plans that are outstanding at the end of each period presented. 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 June 30, Six Months Ended June 30, In thousands, except per share data 2019 2018 2019 2018 Net Income (loss) from continuing operations $ 2,051 $ (339 ) $ 45,469 $ 41,672 Loss from discontinued operations, net of tax (956 ) (659 ) (1,173 ) (1,133 ) Net income (loss) $ 1,095 $ (998 ) $ 44,296 $ 40,539 Average common shares outstanding - basic 29,337 28,791 29,123 28,772 Additional shares for stock-based compensation plans (See Note 8) 57 — 63 53 Average common shares outstanding - diluted 29,394 28,791 29,186 28,825 Earnings (loss) from continuing operations per share of common stock: Basic $ 0.07 $ (0.01 ) $ 1.56 $ 1.45 Diluted $ 0.07 $ (0.01 ) $ 1.56 $ 1.45 Loss from discontinued operations per share of common stock: Basic $ (0.03 ) $ (0.02 ) $ (0.04 ) $ (0.04 ) Diluted $ (0.03 ) $ (0.02 ) $ (0.04 ) $ (0.04 ) Earnings (loss) per share of common stock: Basic $ 0.04 $ (0.03 ) $ 1.52 $ 1.41 Diluted $ 0.04 $ (0.03 ) $ 1.52 $ 1.41 Additional information: Anti-dilutive shares 1 53 2 10

Segment Information

Segment Information	6 Months Ended
	Jun. 30, 2019
Segment Reporting [Abstract]
Segment Information	SEGMENT INFORMATION We primarily operate in one reportable business segment, which is NW Natural's local gas distribution business and is referred to as the NGD s egment. During the second quarter of 2018, we moved forward with long-term strategic plans, which include a shift away from the California gas storage business, by entering into a Purchase and Sale Agreement that provides for the sale of all of the membership interests in Gill Ranch, subject to various regulatory approvals and closing conditions. As such, we reevaluated reportable segments and concluded that the remaining gas storage activities no longer meet the requirements of a reportable segment. Interstate Storage Services and asset management activities at the Mist gas storage facility, are now reported as other under NW Natural. NW Natural and NW Holdings also have investments and b usiness activities not specifically related to the NGD, which are aggregated and reported as other and described below for each entity. Natural Gas Distribution NW Natural's local gas distribution segment is a regulated utility principally engaged in the purchase, sale, and delivery of natural gas and related services to customers in Oregon and southwest Washington. In addition to NW Natural's local gas distribution business, the NGD segment also includes the portion of the Mist underground storage facility used to serve NGD customers, the North Mist gas storage expansion in Oregon, and NWN Gas Reserves, which is a wholly-owned subsidiary of Energy Corp. NW Natural NW Natural's activities in Other include Interstate Storage Services and third-party asset management services for the Mist facility in Oregon, appliance retail center operations, and corporate operating and non-operating revenues and expenses that cannot be allocated to NGD operations. Earnings from Interstate Storage Services assets are primarily related to firm storage capacity revenues. Earnings from the Mist facility also include revenue, net of amounts shared with NGD customers, from management of NGD assets at Mist and upstream pipeline capacity when not needed to serve NGD customers. Under the Oregon sharing mechanism, NW Natural retains 80% of the pre-tax income from these services when the costs of the capacity were not included in NGD rates, or 10% of the pre-tax income when the costs have been included in these rates. The remaining 20% and 90% , respectively, are recorded in a deferred regulatory account for crediting back to NGD customers. NW Holdings NW Holdings' activities in Other include all remaining activities not associated with NW Natural, specifically: NWN Water, which consolidates the water and wastewater 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 14 . Other also includes corporate revenues and expenses that cannot be allocated to other operations . All prior period amounts have been retrospectively adjusted to reflect the change in reportable segments and the designation of Gill Ranch as a discontinued operation for NW Holdings, and the designation of subsidiaries previously owned by NW Natural that are now owned by NW Holdings as discontinued operations for NW Natural. Segment Information Summary Inter-segment transactions were immaterial for the periods presented. The following table presents summary financial information concerning the reportable segments of continuing operations. See Note 18 for information regarding discontinued operations for NW Holdings and NW Natural. Three Months Ended June 30, In thousands NGD Other (NW Natural) NW Natural Other (NW Holdings) NW Holdings 2019 Operating revenues $ 117,984 $ 4,258 $ 122,242 $ 1,201 $ 123,443 Depreciation and amortization 21,992 251 22,243 144 22,387 Income (loss) from operations 14,657 2,583 17,240 (1,142 ) 16,098 Net income (loss) from continuing operations 1,212 1,842 3,054 (1,003 ) 2,051 Capital expenditures 41,912 105 42,017 366 42,383 2018 Operating revenues $ 118,515 $ 6,048 $ 124,563 $ 4 $ 124,567 Depreciation and amortization 20,766 324 21,090 57 21,147 Income (loss) from operations 4,545 3,860 8,405 (136 ) 8,269 Net income (loss) from continuing operations (2,970 ) 2,699 (271 ) (68 ) (339 ) Capital expenditures 43,801 1,240 45,041 — 45,041 Six Months Ended June 30, In thousands NGD Other (NW Natural) NW Natural Other (NW Holdings) NW Holdings 2019 Operating revenues $ 397,025 $ 10,063 $ 407,088 $ 1,703 $ 408,791 Depreciation and amortization 43,241 506 43,747 212 43,959 Income (loss) from operations 87,555 6,329 93,884 (1,741 ) 92,143 Net income (loss) from continuing operations 42,418 4,531 46,949 (1,480 ) 45,469 Capital expenditures 90,518 157 90,675 472 91,147 Total assets at June 30, 2019 (1) 3,089,944 48,749 3,138,693 85,437 3,224,130 2018 Operating revenues $ 376,448 $ 11,750 $ 388,198 $ 4 $ 388,202 Depreciation and amortization 41,309 649 41,958 64 42,022 Income from operations 69,301 6,842 76,143 (123 ) 76,020 Net income (loss) from continuing operations 36,913 4,830 41,743 (71 ) 41,672 Capital expenditures 100,695 1,675 102,370 — 102,370 Total assets at June 30, 2018 (1) 2,907,936 51,993 2,959,929 14,088 2,974,017 Total assets at December 31, 2018 (1) 3,141,969 50,767 3,192,736 36,657 3,229,393 (1) Total assets for NW Holdings exclude assets related to discontinued operations of $14.0 million , $12.7 million , and $13.3 million as of June 30, 2019 , June 30, 2018 , and December 31, 2018 , respectively. Total assets for NW Natural exclude assets related to discontinued operations of $30.9 million as of June 30, 2018 . Natural Gas Distribution Margin NGD margin is a financial measure used by the Chief Operating Decision Maker (CODM) , consisting of NGD operating revenues, reduced by the associated cost of gas, environmental remediation expense, and revenue taxes. The cost of gas purchased for NGD customers is generally a pass-through cost in the amount of revenues billed to regulated NGD customers. Environmental remediation expense represents collections received from customers through the environmental recovery mechanism in Oregon as well as adjustments for the environmental earnings test. This is offset by environmental remediation expense presented in in operating expenses. Revenue taxes are collected from NGD customers and remitted to taxing authorities. The collections from customers are offset by the expense recognition of the obligation to the taxing authority. By subtracting cost of gas, environmental remediation expense, and revenue taxes from NGD operating revenues, NGD margin provides a key metric used by the CODM in assessing the performance of the NGD segment. The following table presents additional segment information concerning NGD margin: Three Months Ended June 30, Six Months Ended June 30, In thousands 2019 2018 2019 2018 NGD margin calculation: NGD distribution revenues $ 115,792 $ 118,435 $ 394,775 $ 376,341 Other regulated services 2,192 80 2,250 107 Total NGD operating revenues 117,984 118,515 397,025 376,448 Less: NGD cost of gas 35,163 42,107 140,676 150,271 Environmental remediation (2,656 ) 1,882 6,291 6,506 Revenue taxes 4,496 4,780 16,422 17,209 NGD margin $ 80,981 $ 69,746 $ 233,636 $ 202,462

Common Stock (Notes)

Common Stock (Notes)	6 Months Ended
	Jun. 30, 2019
Common Stock [Abstract]
Stockholders' Equity Note Disclosure	COMMON STOCK During June 2019 , NW Holdings completed an equity issuance consisting of an offering of 1,250,000 shares of its common stock along with a 30 -day option for the underwriters to purchase an additional 187,500 shares. The offering closed on June 7, 2019 and resulted in a total issuance of 1,437,500 shares as both the initial offering and the underwriter option were fully executed. All shares were issued on June 7, 2019 at an offering price of $67.00 per share. The issuance resulted in proceeds to NW Holdings, net of $0.4 million in estimated expenses, of $92.8 million . The issuance was executed to raise funds for general corporate purposes, including for NW Holdings’ subsidiaries, that are reflected as equity transfers on occurrence. During the period, contributions received by NW Natural were also used, in part, to repay short-term indebtedness.

Leases (Notes)

Leases (Notes)	6 Months Ended
	Jun. 30, 2019
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: In thousands Three months ended June 30, 2019 Six months ended June 30, 2019 Lease revenue Operating leases $ 47 $ 95 Sales-type leases 2,085 2,145 Total lease revenue $ 2,132 $ 2,240 Total future minimum lease payments to be received under non-cancelable leases at NW Natural at June 30, 2019 are as follows: In thousands Operating Sales-Type Total Remainder of 2019 $ 58 $ 9,708 $ 9,766 2020 61 18,228 18,289 2021 49 17,518 17,567 2022 45 17,026 17,071 2023 45 16,557 16,602 Thereafter 138 280,607 280,745 Total lease revenue $ 396 $ 359,644 $ 360,040 Less: imputed interest 208,877 Total leases receivable $ 150,767 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 at June 30, 2019 was $3.8 million 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 headquarters. Our leases have remaining lease terms of one year to 11 years. Many of our lease agreements include options to extend the lease, which we do not include in our minimum lease terms unless they are reasonably certain to be exercised. Short-term leases with a term of 12 months or less are not recorded on the balance sheet. As most of our leases do not provide an implicit rate and are entered into by NW Natural, we use NW Natural's incremental borrowing rate based on information available at the lease commencement date in determining the present value of lease payments. The components of lease expense, a portion of which is capitalized, were as follows: Three months ended June 30, 2019 In thousands NW Natural Other NW Holdings Operating lease expense $ 1,155 $ 46 $ 1,201 Short-term lease expense 331 — 331 Six months ended June 30, 2019 In thousands NW Natural Other NW Holdings Operating lease expense $ 2,297 $ 92 $ 2,389 Short-term lease expense 491 — 491 Supplemental balance sheet information related to operating leases as of June 30, 2019 is as follows: In thousands NW Natural Other NW Holdings Operating lease right of use asset $ 4,797 $ 216 $ 5,013 Operating lease liabilities - current liabilities $ 4,141 $ 130 $ 4,271 Operating lease liabilities - non-current liabilities 634 87 721 Total operating lease liabilities $ 4,775 $ 217 $ 4,992 As of June 30, 2019 , the weighted average remaining lease term for the operating leases is 1.06 years for NW Natural. The weighted average discount rate used in the valuation of the operating lease right of use assets over the remaining lease term is 3.82% for NW Natural. Maturities of operating lease liabilities at June 30, 2019 were as follows: In thousands NW Natural Other NW Holdings Remainder of 2019 $ 2,298 $ 93 $ 2,391 2020 1,980 102 2,082 2021 101 28 129 2022 93 — 93 2023 71 — 71 Thereafter 497 — 497 Total lease payments 5,040 223 5,263 Less: imputed interest 265 6 271 Total lease obligations 4,775 217 4,992 Less: current obligations 4,141 130 4,271 Long-term lease obligations $ 634 $ 87 $ 721 Significant Lease Not Yet Commenced In October 2017, NW Natural entered into a 20 -year operating lease agreement for a new headquarters in Portland, Oregon in anticipation of the expiration of the current headquarters lease in 2020. The lease is expected to commence when construction of the asset is completed in early 2020. Total estimated base rent payments over the life of the lease are approximately $160 million . There is an option to extend the term of the lease for two additional periods of seven years . Cash Flow Information Supplemental cash flow information related to leases was as follows: Three months ended June 30, 2019 In thousands NW Natural Other NW Holdings Cash paid for amounts included in the measurement of lease liabilities Operating cash flows from operating leases $ 1,115 $ 44 $ 1,159 Six months ended June 30, 2019 NW Natural Other NW Holdings Cash paid for amounts included in the measurement of lease liabilities Operating cash flows from operating leases $ 2,206 $ 87 $ 2,293 Right of use assets obtained in exchange for lease obligations Operating leases $ 6,987 $ 304 $ 7,291 Finance Leases NW Natural also leases building storage spaces for use as a gas meter room in order to provide natural gas to multifamily or mixed use developments. These contracts are accounted for as finance leases and typically involve a one-time upfront payment with no remaining liability. The right of use asset for finance leases was $0.3 million at June 30, 2019 . Lease Disclosures Related to Periods Prior to the First Quarter of 2019 Land, buildings, and equipment are leased under agreements that expire in various years, including a 99-year land lease that extends through 2108. Rental costs for continuing operations were $5.9 million , $7.3 million , and $5.9 million for the years ended December 31, 2018 , 2017 , and 2016 , respectively, a portion of which was capitalized. The following table reflects NW Natural's future minimum lease payments due under non-cancelable operating leases for continuing operations at December 31, 2018 . These commitments relate principally to the lease of the office headquarters and underground gas storage facilities. In thousands Minimum lease payments 2019 $ 5,368 2020 4,812 2021 7,077 2022 7,223 2023 7,304 Thereafter 149,881 Total $ 181,665

Revenue (Notes)

Revenue (Notes)	6 Months Ended
	Jun. 30, 2019
Revenue from Contract with Customer [Abstract]
Revenue from Contract with Customer	REVENUE The following tables present disaggregated revenue from continuing operations: Three Months Ended June 30, In thousands NGD Other (NW Natural) NW Natural Other (NW Holdings) NW Holdings 2019 Natural gas sales $ 112,015 $ — $ 112,015 $ — $ 112,015 Gas storage revenue, net — 2,740 2,740 — 2,740 Asset management revenue, net — 460 460 — 460 Appliance retail center revenue — 1,058 1,058 — 1,058 Other revenue 104 — 104 1,201 1,305 Revenue from contracts with customers 112,119 4,258 116,377 1,201 117,578 Alternative revenue 3,733 — 3,733 — 3,733 Leasing revenue 2,132 — 2,132 — 2,132 Total operating revenues $ 117,984 $ 4,258 $ 122,242 $ 1,201 $ 123,443 2018 Natural gas sales $ 114,726 $ — $ 114,726 $ — $ 114,726 Gas storage revenue, net — 2,737 2,737 — 2,737 Asset management revenue, net — 2,140 2,140 — 2,140 Appliance retail center revenue — 1,171 1,171 — 1,171 Other revenue — — — 4 4 Revenue from contracts with customers 114,726 6,048 120,774 4 120,778 Alternative revenue 3,663 — 3,663 — 3,663 Leasing revenue 126 — 126 — 126 Total operating revenues $ 118,515 $ 6,048 $ 124,563 $ 4 $ 124,567 Six Months Ended June 30, In thousands NGD Other (NW Natural) NW Natural Other (NW Holdings) NW Holdings 2019 Natural gas sales $ 408,201 $ — $ 408,201 $ — $ 408,201 Gas storage revenue, net — 5,523 5,523 — 5,523 Asset management revenue, net — 1,966 1,966 — 1,966 Appliance retail center revenue — 2,574 2,574 — 2,574 Other revenue 104 — 104 1,703 1,807 Revenue from contracts with customers 408,305 10,063 418,368 1,703 420,071 Alternative revenue (13,520 ) — (13,520 ) — (13,520 ) Leasing revenue 2,240 — 2,240 — 2,240 Total operating revenues $ 397,025 $ 10,063 $ 407,088 $ 1,703 $ 408,791 2018 Natural gas sales $ 372,954 $ — $ 372,954 $ — $ 372,954 Gas storage revenue, net — 5,314 5,314 — 5,314 Asset management revenue, net — 3,719 3,719 — 3,719 Appliance retail center revenue — 2,717 2,717 — 2,717 Other revenue — — — 4 4 Revenue from contracts with customers 372,954 11,750 384,704 4 384,708 Alternative revenue 3,291 — 3,291 — 3,291 Leasing revenue 203 — 203 — 203 Total operating revenues $ 376,448 $ 11,750 $ 388,198 $ 4 $ 388,202 NW Natural's revenue represents substantially all of NW Holdings' revenue and is recognized for both registrants when the obligation to customers is satisfied and in the amount expected to be received in exchange for transferring goods or providing services. Revenue from contracts with customers contains one performance obligation that is generally satisfied over time, using the output method based on time elapsed, due to the continuous nature of the service provided. The transaction price is determined by a set price agreed upon in the contract or dependent on regulatory tariffs. Customer accounts are settled on a monthly basis or paid at time of sale and based on historical experience. It is probable that we will collect substantially all of the consideration to which we are entitled. NW Holdings and NW Natural do not have any material contract assets, as net accounts receivable and accrued unbilled revenue balances are unconditional and only involve the passage of time until such balances are billed and collected. NW Holdings and NW Natural do not have any material contract liabilities. Revenue-based taxes are primarily franchise taxes, which are collected from NGD customers and remitted to taxing authorities. Beginning January 1, 2018, revenue taxes are included in operating revenues with an equal and offsetting expense recognized in operating expenses in the consolidated statements of comprehensive income. Natural Gas Distribution Natural gas sales. NW Natural's primary source of revenue is providing natural gas to customers in the NGD service territory, which includes residential, commercial, industrial and transportation customers. NGD revenue is generally recognized over time upon delivery of the gas commodity or service to the customer, and the amount of consideration received and recognized as revenue is dependent on the Oregon and Washington tariffs. Customer accounts are to be paid in full each month, and there is no right of return or warranty for services provided. Revenues include firm and interruptible sales and transportation services, franchise taxes recovered from the customer, late payment fees, service fees, and accruals for gas delivered but not yet billed (accrued unbilled revenue). The accrued unbilled revenue balance is based on estimates of deliveries during the period from the last meter reading and management judgment is required for a number of factors used in this calculation, including customer use and weather factors. We applied the significant financing practical expedient and have not adjusted the consideration NW Natural expects to receive from NGD customers for the effects of a significant financing component as all payment arrangements are settled annually. Due to the election of the right to invoice practical expedient, we do not disclose the value of unsatisfied performance obligations as of June 30, 2019 . Alternative revenue. Weather normalization (WARM) and decoupling mechanisms are considered to be alternative revenue programs. Alternative revenue programs are considered to be contracts between NW Natural and its regulator and are excluded from revenue from contracts with customers. Leasing revenue. Leasing revenue primarily consists of 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 7 . NW Natural Other Gas storage revenue. NW Natural's other revenue includes gas storage activity, which includes Interstate Storage Services used to store natural gas for customers. Gas storage revenue is generally recognized over time as the gas storage service is provided to the customer and the amount of consideration received and recognized as revenue is dependent on set rates defined per the storage agreements. Noncash consideration in the form of dekatherms of natural gas is received as consideration for providing gas injection services to gas storage customers. This noncash consideration is measured at fair value using the average spot rate. Customer accounts are generally paid in full each month, and there is no right of return or warranty for services provided. Revenues include firm and interruptible storage services, net of the profit sharing amount refunded to NGD customers. Asset management revenue. Asset management revenue is generally recognized over time using a straight-line approach over the term of each contract, and the amount of consideration received and recognized as revenue is dependent on a variable pricing model. Variable revenues earned above guaranteed amounts are estimated and recognized at the end of each period using the most likely amount approach. Revenues include management services of the storage assets and pipeline capacity provided, net of the profit sharing amount refunded to NGD customers. Asset management accounts are settled on a monthly basis. As of June 30, 2019 , unrecognized revenue for the fixed component of the transaction price related to gas storage and asset management revenue was approximately $58.4 million . Of this amount, approximately $7.4 million will be recognized during the remainder of 2019 , $13.7 million in 2020 , $12.8 million in 2021 , $9.1 million in 2022 , $7.8 million in 2023 and $7.5 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 and Idaho tariffs. Customer accounts are to be paid in full each month, and there is no right of return or warranty for services provided. We applied the significant financing practical expedient and have not adjusted the consideration we expect to receive from water distribution customers for the effects of a significant financing component as all payment arrangements are settled annually. Due to the election of the right to invoice practical expedient, we do not disclose the value of unsatisfied performance obligations as of June 30, 2019 .

Stock-Based Compensation

Stock-Based Compensation	6 Months Ended
	Jun. 30, 2019
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	STOCK-BASED COMPENSATION Stock-based compensation plans are designed to promote stock ownership in NW Holdings by employees and officers. These compensation plans include a Long Term Incentive Plan (LTIP), an Employee Stock Purchase Plan (ESPP), and a Restated Stock Option Plan. For additional information on stock-based compensation plans, see Note 7 in the 2018 Form 10-K and the updates provided below. Long Term Incentive Plan Performance Shares LTIP performance shares incorporate a combination of market, performance, and service-based factors. During the six months ended June 30, 2019 , no performance-based shares were granted under the LTIP for accounting purposes. In February 2019 and 2018, LTIP shares were awarded to participants; however, the agreements allow for one of the performance factors to remain variable until the first quarter of the third year of the award period. As the performance factor will not be approved until the first quarters of 2021 and 2020, respectively, there is not a mutual understanding of the awards' key terms and conditions between NW Holdings and the participants as of June 30, 2019 , and therefore, no expense was recognized for the 2019 and 2018 awards. NW Holdings will calculate the grant date fair value and NW Natural and other subsidiaries will recognize expense over the remaining service period for each award once the final performance factor has been approved. For the 2019 and 2018 LTIP awards, share payouts range from a threshold of 0% to a maximum of 200% based on achievement of pre-established goals. The performance criteria for the 2019 and 2018 performance shares consists of a three-year Return on Invested Capital (ROIC) threshold that must be satisfied and a cumulative EPS factor, which can be modified by a total shareholder return factor (TSR modifier) relative to the performance of the Russell 2500 Utilities Index over the performance period of three years for each respective award. If the targets were achieved for the 2019 and 2018 awards, NW Holdings would grant 36,250 and 32,497 shares in the first quarters of 2021 and 2020, respectively. As of June 30, 2019 , there was $0.6 million of unrecognized compensation cost associated with the 2017 LTIP grants, which is expected to be recognized through 2019 . Restricted Stock Units During the six months ended June 30, 2019 , 33,804 RSUs were granted under the LTIP with a weighted-average grant date fair value of $64.93 per share. Generally, the RSUs awarded are forfeitable and include a performance-based threshold as well as a vesting period of four years from the grant date. Generally, an RSU obligates NW Holdings, upon vesting, to issue the RSU holder one share of common stock plus a cash payment equal to the total amount of dividends paid per share between the grant date and vesting date of that portion of the RSU. The fair value of an RSU is equal to the closing market price of common stock on the grant date. As of June 30, 2019 , there was $ 4.0 million of unrecognized compensation cost from grants of RSUs, which is expected to be recognized by NW Natural and other subsidiaries over a period extending through 2023

Debt

Debt	6 Months Ended
	Jun. 30, 2019
Debt Disclosure [Abstract]
Debt	DEBT Short-Term Debt At June 30, 2019 , NW Holdings had short-term debt outstanding of $20.1 million and NW Natural had no commercial paper outstanding. The carrying cost of commercial paper approximates fair value using Level 2 inputs. See Note 2 in the 2018 Form 10-K for a description of the fair value hierarchy. Long-Term Debt At June 30, 2019 , NW Holdings and NW Natural had long-term debt outstanding of $910.4 million and $873.3 million , respectively, which included $6.4 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 2019 through 2049 , interest rates ranging from 2.822% to 9.050% , and a weighted average interest rate of 4.786% . In June 2019 , NW Natural issued $90.0 million of FMBs with an interest rate of 3.869% , due in 2049 and $50.0 million of FMBs with an interest rate of 3.141% , due in 2029 . 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 carries an interest rate based upon the three-month LIBOR rate, which at June 30, 2019 was 2.86% . 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 June 30, 2019 , with a consolidated indebtedness to total capitalization ratio of 51.5% . 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 2018 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 June 30, December 31, In thousands 2019 2018 2018 Gross long-term debt $ 916,832 $ 764,700 $ 741,813 Unamortized debt issuance costs (6,435 ) (6,020 ) (5,577 ) Carrying amount $ 910,397 $ 758,680 $ 736,236 Estimated fair value (1) $ 970,205 $ 792,623 $ 762,335 (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 June 30, December 31, In thousands 2019 2018 2018 Gross long-term debt $ 879,700 $ 764,700 $ 739,700 Unamortized debt issuance costs (6,394 ) (6,020 ) (5,577 ) Carrying amount $ 873,306 $ 758,680 $ 734,123 Estimated fair value (1) $ 933,167 $ 792,623 $ 760,222 (1) Estimated fair value does not include unamortized debt issuance costs.

Pension and Other Postretiremen

Pension and Other Postretirement Benefit Costs	6 Months Ended
	Jun. 30, 2019
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, 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 qualified defined benefit 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 June 30, Six Months Ended June 30, Pension Benefits Other Postretirement Benefits Pension Benefits Other Postretirement Benefits In thousands 2019 2018 2019 2018 2019 2018 2019 2018 Service cost $ 1,516 $ 1,807 $ 67 $ 79 $ 3,033 $ 3,614 $ 135 $ 159 Interest cost 4,661 4,183 283 241 9,323 8,366 564 482 Expected return on plan assets (5,207 ) (5,150 ) — — (10,414 ) (10,301 ) — — Amortization of prior service costs 2 10 (117 ) (117 ) 4 21 (234 ) (234 ) Amortization of net actuarial loss 3,603 4,524 96 112 7,206 9,047 193 222 Net periodic benefit cost 4,575 5,374 329 315 9,152 10,747 658 629 Amount allocated to construction (596 ) (685 ) (23 ) (28 ) (1,182 ) (1,367 ) (47 ) (55 ) Amount deferred to regulatory balancing account — (2,747 ) — — — (5,503 ) — — Net periodic benefit cost charged to expense 3,979 1,942 306 287 7,970 3,877 611 574 Regulatory pension disallowance — — — — 10,500 — — — Amortization of regulatory balancing account 1,281 — — — 13,792 — — — Net amount charged to expense $ 5,260 $ 1,942 $ 306 $ 287 $ 32,262 $ 3,877 $ 611 $ 574 The service cost component of net periodic benefit costs is reduced by amounts capitalized to NGD plant based on an approximately 25% to 35% payroll overhead charge. In addition, a certain amount of net periodic benefit costs were recorded to the regulatory balancing account, representing net periodic pension expense for the qualified plan above the amount set in rates, as approved by the OPUC, from 2011 through October 31, 2018. In March 2019, the OPUC issued an order concluding the NW Natural 2018 Oregon rate case. 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 June 30, Six Months Ended June 30, In thousands 2019 2018 2019 2018 Beginning balance $ (8,439 ) $ (8,284 ) $ (7,188 ) $ (8,438 ) Amounts reclassified from AOCL: Amortization of actuarial losses 156 209 312 418 Reclassification of stranded tax effects (1) — — (1,366 ) — Total reclassifications before tax 156 209 (1,054 ) 418 Tax (benefit) expense (41 ) (56 ) (82 ) (111 ) Total reclassifications for the period 115 153 (1,136 ) 307 Ending balance $ (8,324 ) $ (8,131 ) $ (8,324 ) $ (8,131 ) (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 six months ended June 30, 2019 , NW Natural made cash contributions totaling $4.7 million to qualified defined benefit pension plans. NW Natural expects further plan contributions of $6.3 million during the remainder of 2019 . Defined Contribution Plan The Retirement K Savings Plan is a qualified defined contribution plan under Internal Revenue Code Sections 401(a) and 401(k). Employer contributions totaled $3.8 million and $3.5 million for the six months ended June 30, 2019 and 2018 , respectively. See Note 9 in the 2018 Form 10-K for more information concerning these retirement and other postretirement benefit plans.

Income Tax

Income Tax	6 Months Ended
	Jun. 30, 2019
Income Tax Disclosure [Abstract]
Income Tax	INCOME TAX An estimate of annual income tax expense is made each interim period using estimates for annual pre-tax income, regulatory flow-through adjustments, tax credits, and other items. The estimated annual effective tax rate is applied to year-to-date, pre-tax income to determine income tax expense for the interim period consistent with the annual estimate. Discrete events are recorded in the interim period in which they occur or become known. The effective income tax rate varied from the combined federal and state statutory tax rates due to the following: Three Months Ended June 30, NW Holdings NW Natural In thousands 2019 2018 2019 2018 Income taxes at statutory rates (federal and state) $ 694 $ (135 ) $ 1,055 $ (107 ) Increase (decrease): Differences required to be flowed-through by regulatory commissions (37 ) (14 ) (37 ) (14 ) Other, net (32 ) (7 ) (33 ) (7 ) Total provision for income taxes on continuing operations $ 625 $ (156 ) $ 985 $ (128 ) Effective tax rate for continuing operations 23.4 % 31.5 % 24.4 % 32.1 % Six Months Ended June 30, NW Holdings NW Natural In thousands 2019 2018 2019 2018 Income taxes at statutory rates (federal and state) $ 15,007 $ 15,233 $ 15,540 $ 15,264 Increase (decrease): Differences required to be flowed-through by regulatory commissions (5,297 ) 835 (5,297 ) 835 Other, net (410 ) (592 ) (410 ) (592 ) Total provision for income taxes on continuing operations $ 9,300 $ 15,476 $ 9,833 $ 15,507 Effective tax rate for continuing operations 17.0 % 27.1 % 17.3 % 27.1 % The NW Holdings and NW Natural effective income tax rate for the three and six months ended June 30, 2019 compared to the same periods in 2018 changed primarily as a result of regulatory amortization of deferred TCJA benefits as approved in the March 2019 OPUC order. See " U.S. Federal TCJA Matters" below and Note 10 in the 2018 Form 10-K for more detail on income taxes and effective tax rates. The IRS Compliance Assurance Process (CAP) examination of the 2017 tax year was completed during the first quarter of 2019. There were no material changes to the return as filed. The 2018 tax year is subject to examination under CAP and the 2019 tax year CAP application has been accepted by the IRS. The Oregon State examination of tax years 2015, 2016, and 2017 was completed in January 2019. There were no material changes to the returns as originally filed. U.S. Federal TCJA Matters On December 22, 2017, the TCJA was enacted and permanently lowered the U.S. federal corporate income tax rate to 21% from the previous maximum rate of 35% , effective for the tax year beginning January 1, 2018. The TCJA included specific provisions related to regulated public utilities that provide for the continued deductibility of interest expense and the elimination of bonus tax depreciation for property both acquired and placed into service on or after January 1, 2018. See Note 10 in the 2018 Form 10-K. NW Natural previously filed applications with the OPUC and WUTC to defer the NGD net income tax benefits resulting from the TCJA. In March 2019, the OPUC issued an order addressing the regulatory amortization of the income tax benefits from the TCJA that NW Natural deferred for Oregon customers in December of 2017. Under the order, NW Natural will provide the benefit of these TCJA income tax deferrals to Oregon customers through ongoing annual credits to customer base rates and as a one-time recovery of a portion of the pension balancing account regulatory asset balance. On an annualized basis, it is anticipated that the income tax benefits from the provision of these TCJA benefits to customers should approximate the reduction to pretax income that occurs as a result of the customer base rate credits and one-time recovery of a portion of the pension balancing account. The resolution of deferred TCJA income tax benefits for Washington customers is expected later this year as part of NW Natural's Washington general rate case.

Property, Plant and Equipment (

Property, Plant and Equipment (Notes)	6 Months Ended
	Jun. 30, 2019
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment Disclosure [Text Block]	PROPERTY, PLANT, AND EQUIPMENT The following table sets forth the major classifications of property, plant, and equipment and accumulated depreciation of continuing operations: June 30, December 31, In thousands 2019 2018 2018 NW Natural: NGD plant in service $ 3,193,121 $ 3,035,089 $ 3,134,122 NGD work in progress 75,045 192,496 204,978 Less: Accumulated depreciation 997,111 966,766 974,252 NGD plant, net 2,271,055 2,260,819 2,364,848 Other plant in service 63,385 65,548 66,009 Other construction work in progress 5,454 5,347 5,330 Less: Accumulated depreciation 18,650 18,024 18,603 Other plant, net (1) 50,189 52,871 52,736 Total property, plant, and equipment $ 2,321,244 $ 2,313,690 $ 2,417,584 Other (NW Holdings): Other plant in service $ 18,806 $ 376 $ 4,051 Less: Accumulated depreciation 424 208 263 Other plant, net (1) $ 18,382 $ 168 $ 3,788 NW Holdings: Total property, plant, and equipment $ 2,339,626 $ 2,313,858 $ 2,421,372 NW Natural and NW Holdings: Capital expenditures in accrued liabilities $ 32,923 $ 22,112 $ 23,676 (1) NW Natural p reviously reported other balances were restated due to certain assets and liabilities now being classified as discontinued operations assets and liabilities in its balance sheets. See Note 18 for further discussion. NW Holdings Other plant balances include long-lived assets associated with water operations and non-regulated activities not held by NW Natural or its subsidiaries. NW Natural Other plant balances include long-lived assets not related to NGD. In October 2017, NW Natural entered into a 20 -year operating lease agreement expected to commence in 2020 for its new headquarters location in Portland, Oregon. Under the new lease standard, NW Natural is no longer considered the accounting owner of the asset during construction. As such, the build to suit asset and liability balances at December 31, 2018 of $26.0 million were derecognized in January 2019. The previous build to suit balances were recorded under ASC 840 within property, plant and equipment and other non-current liabilities in the consolidated balance sheet. See Note 16 in the 2018 Form 10-K. 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 7 for information regarding leases, including North Mist.

Gas Reserves

Gas Reserves	6 Months Ended
	Jun. 30, 2019
Gas Reserves [Abstract]
Gas Reserves	GAS RESERVES NW Natural has invested $188 million through the gas reserves program in the Jonah Field located in Wyoming as of June 30, 2019 . Gas reserves are stated at cost, net of regulatory amortization, with the associated deferred tax benefits recorded as liabilities in the consolidated balance sheets. The investment in gas reserves provides long-term price protection for NGD customers through the original agreement with Encana Oil & Gas (USA) Inc. under which NW Natural invested $178 million and the amended agreement with Jonah Energy LLC under which an additional $10 million was invested. The cost of gas, including a carrying cost for the rate base investment, is included in the annual Oregon PGA filing, which allows NW Natural to recover these costs through customer rates. The investment under the original agreement, less accumulated amortization and deferred taxes, earns a rate of return. See Note 12 in the 2018 Form 10-K. Gas produced from the additional wells is included in the Oregon PGA at a fixed rate of $0.4725 per therm, which approximates the 10 -year hedge rate plus financing costs at the inception of the investment. The following table outlines NW Natural's net gas reserves investment: June 30, December 31, In thousands 2019 2018 2018 Gas reserves, current $ 17,206 $ 16,579 $ 16,647 Gas reserves, non-current 170,101 170,958 170,660 Less: Accumulated amortization 113,930 95,596 104,463 Total gas reserves (1) 73,377 91,941 82,844 Less: Deferred taxes on gas reserves 26,995 20,381 20,071 Net investment in gas reserves $ 46,382 $ 71,560 $ 62,773 (1) The net investment in additional wells included in total gas reserves was $ 4.3 million , $ 5.5 million and $ 4.8 million at June 30, 2019 and 2018 and December 31, 2018 , respectively. NW Natural's investment is included in NW Holdings' and NW Natural's consolidated balance sheets under gas reserves with the maximum loss exposure limited to the investment balance.

Investments

Investments	6 Months Ended
	Jun. 30, 2019
Investments [Abstract]
Investments	INVESTMENTS Investments in Gas Pipeline Trail West Pipeline, LLC (TWP), a wholly-owned subsidiary of TWH, is pursuing the development of a new gas transmission pipeline that would provide an interconnection with NW Natural's NGD system. NWN Energy, a wholly-owned subsidiary of NW Holdings, owns 50% of TWH, and 50% is owned by TransCanada American Investments Ltd., an indirect wholly-owned subsidiary of TransCanada Corporation. Variable Interest Entity (VIE) Analysis TWH is a VIE, with NW Holdings' investment in TWP reported under equity method accounting. It has been determined that NW Holdings is not the primary beneficiary of TWH’s activities as it only has a 50% share of the entity, and there are no stipulations that allow NW Holdings a disproportionate influence over it. Investments in TWH and TWP are included in other investments in NW Holdings' balance sheet. If this investment is not developed, then the maximum loss exposure related to TWH is limited to NW Holdings' equity investment balance, less its share of any cash or other assets available to NW Holdings as a 50% owner. The investment balance in TWH was $13.4 million at June 30, 2019 and 2018 and December 31, 2018 . See Note 13 in the 2018 Form 10-K. Other Investments Other investments include financial investments in life insurance policies, which are accounted for at cash surrender value, net of policy loans. See Note 13 in the 2018

Business Combinations Business

Business Combinations Business Combinations	6 Months Ended
	Jun. 30, 2019
Business Combinations [Abstract]
Business Combination Disclosure	BUSINESS COMBINATIONS 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 was approximately $55.2 million in cash consideration, subject to closing adjustments. The transaction aligns with NW Holdings' water sector strategy as the Company 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 market and regulatory conditions as well as standard valuation approaches in order to allocate value as determined by an independent third party assessor for certain assets, with the remaining difference from the consideration transferred being recorded as goodwill. This allocation is considered preliminary as of June 30, 2019 , 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, contract assets and liabilities, working capital adjustments, 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 $40.2 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 $50.7 million . The preliminary purchase price for the acquisition has been allocated to the assets acquired as of the acquisition date and is as follows: In thousands May 31, 2019 Current assets $ 211 Property, plant and equipment 14,009 Goodwill 40,153 Deferred tax assets 828 Total assets acquired $ 55,201 The amount of Sunriver revenues included in NW Holdings' consolidated statements of comprehensive income is $0.6 million for the three and six months ended June 30, 2019 . Earnings from Sunriver activities for the three and six months ended June 30, 2019 were not material to the results of NW Holdings. Other Acquisitions During 2019 , NWN Water completed one additional acquisition qualifying as a business combination. The aggregate fair value of the preliminary consideration transferred for this acquisition was approximately $0.7 million . This business combination was not significant to NW Holdings' results of operations. 2018 Business Combinations Falls Water On September 13, 2018 , NWN Water, then a wholly-owned subsidiary of NW Natural and now a wholly-owned subsidiary of NW Holdings, completed the acquisition of Falls Water Co., Inc. (Falls Water), a privately-owned water utility in the Pacific Northwest for preliminary non-cash consideration of $8.5 million , subject to closing adjustments, in the form of 125,000 shares of NW Natural common stock, which were converted to NW Holdings common stock in our October 1, 2018 reorganization. Falls Water became a wholly-owned subsidiary of NWN Water and marked its first acquisition in the water utility sector. This acquisition aligns with NW Holdings' water sector strategy as the acquisition provides NWN Water entry into Idaho, expands service area, and opens further opportunity for growth. Falls Water is based in Idaho Falls, Idaho and served approximately 5,300 connections at the time of acquisition. Through the purchase of all of the outstanding shares of Falls Water, NWN Water acquired the net assets and 100% control of Falls Water. We determined that the Falls Water acquisition met the criteria of a business combination, and as such performed a preliminary allocation of the consideration to the acquired assets and assumed liabilities based on their fair value as of the acquisition date, the majority of which was allocated to goodwill. The allocation is considered preliminary, and is primarily associated with tax positions and goodwill. Subsequent adjustments are not expected to be significant, and any such adjustments are expected to be completed within a one-year measurement period. The acquisition costs were insignificant and were expensed as incurred. The results of Falls Water are not material to the consolidated financial results of NW Holdings. Preliminary goodwill of $6.4 million was recognized from this acquisition and is attributable to Falls Water's regulated service territory and experienced workforce as well as the strategic benefits expected from this high-growth service territory. NW Holdings has included this goodwill in other for segment reporting purposes, and it is not deductible for income tax purposes. No intangible assets aside from goodwill were acquired. Other Acquisitions During 2018, in addition to the Falls Water acquisition, NWN Water completed three acquisitions qualifying as business combinations. The aggregate fair value of the preliminary consideration transferred for these acquisitions was approximately $2.8 million . These business combinations, both individually and in aggregate, were not significant to NW Holdings' results of operations. Goodwill 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 in 2018 and 2019, total goodwill was $49.4 million as of June 30, 2019 and $9.0 million as of December 31, 2018 . The increase in the goodwill balance was 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	6 Months Ended
	Jun. 30, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments	DERIVATIVE INSTRUMENTS NW Natural enters into financial derivative contracts to hedge a portion of the NGD segment's natural gas sales requirements. These contracts include swaps, options and combinations of option contracts. These derivative financial instruments are primarily used to manage commodity price variability. A small portion of NW Natural's derivative hedging strategy involves foreign currency exchange contracts. NW Natural enters into these financial derivatives, up to prescribed limits, primarily to hedge price variability related to physical gas supply contracts as well as to hedge spot purchases of natural gas. The foreign currency forward contracts are used to hedge the fluctuation in foreign currency exchange rates for pipeline demand charges paid in Canadian dollars. In the normal course of business, NW Natural also enters into indexed-price physical forward natural gas commodity purchase contracts and options to meet the requirements of NGD customers. These contracts qualify for regulatory deferral accounting treatment. NW Natural also enters into exchange contracts related to the third-party asset management of its gas portfolio, some of which are derivatives that do not qualify for hedge accounting or regulatory deferral, but are subject to NW Natural's regulatory sharing agreement. These derivatives are recognized in operating revenues, net of amounts shared with NGD customers. Notional Amounts The following table presents the absolute notional amounts related to open positions on NW Natural derivative instruments: June 30, December 31, In thousands 2019 2018 2018 Natural gas (in therms): Financial 466,280 473,900 408,850 Physical 564,500 724,450 472,275 Foreign exchange $ 7,552 $ 7,804 $ 6,936 Purchased Gas Adjustment (PGA) Derivatives entered into by NW Natural for the procurement or hedging of natural gas for future gas years generally receive regulatory deferral accounting treatment. In general, commodity hedging for the current gas year is completed prior to the start of the gas year, and hedge prices are reflected in weighted-average cost of gas in the PGA filing. Hedge contracts entered into after the start of the PGA period are subject to the PGA incentive sharing mechanism in Oregon. NW Natural entered the 2018-19 and 2017-18 gas year with forecasted sales volumes hedged at 48% and 49% in financial swap and option contracts, and 24% and 26% in physical gas supplies, respectively. Hedge contracts entered into prior to the PGA filing in September 2018 were included in the PGA for the 2018-19 gas year. Hedge contracts entered into after the PGA filing, and related to subsequent gas years, may be included in future PGA filings and qualify for regulatory deferral. Unrealized and Realized Gain/Loss The following table reflects the income statement presentation for the unrealized gains and losses from NW Natural's derivative instruments, which also represents all derivative instruments at NW Holdings: Three Months Ended June 30, 2019 2018 In thousands Natural gas commodity Foreign exchange Natural gas commodity Foreign exchange Benefit (expense) to cost of gas $ (5,143 ) $ 246 $ 2,658 $ (56 ) Operating revenues (expense) (4,333 ) — 391 — Amounts deferred to regulatory accounts on balance sheet 8,847 (246 ) (2,915 ) 56 Total gain (loss) in pre-tax earnings $ (629 ) $ — $ 134 $ — Six Months Ended June 30, 2019 2018 In thousands Natural gas commodity Foreign exchange Natural gas commodity Foreign exchange Benefit (expense) to cost of gas $ 1,864 $ 157 $ (3,089 ) $ (210 ) Operating revenues (expense) (1,966 ) — 164 — Amounts deferred to regulatory accounts on balance sheet (182 ) (157 ) 2,980 210 Total gain (loss) in pre-tax earnings $ (284 ) $ — $ 55 $ — 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 $0.9 million and net gains of $10.4 million for the three and six months ended June 30, 2019 , from the settlement of natural gas financial derivative contracts. Whereas, net losses of $4.7 million and $13.7 million were realized for the three and six months ended June 30, 2018 . Realized gains and losses offset the higher or lower cost of gas purchased resulting in no incremental amounts to collect or refund to customers. Credit Risk Management of Financial Derivatives Instruments No collateral was posted with or by NW Natural counterparties as of June 30, 2019 or 2018 . NW Natural attempts to minimize the potential exposure to collateral calls by counterparties to manage liquidity risk. Counterparties generally allow a certain credit limit threshold before requiring NW Natural to post collateral against loss positions. Given NW Natural's counterparty credit limits and portfolio diversification, it was not subject to collateral calls in 2019 or 2018 . The collateral call exposure is set forth under credit support agreements, which generally contain credit limits. NW Natural could also be subject to collateral call exposure where it has agreed to provide adequate assurance, which is not specific as to the amount of credit limit allowed, but could potentially require additional collateral in the event of a material adverse change. Based upon current commodity financial swap and option contracts outstanding, which reflect unrealized losses of $4.6 million at June 30, 2019 , we have estimated the level of collateral demands, with and without potential adequate assurance calls, using current gas prices and various credit downgrade rating scenarios for NW Natural as follows: Credit Rating Downgrade Scenarios In thousands (Current Ratings) A+/A3 BBB+/Baa1 BBB/Baa2 BBB-/Baa3 Speculative With Adequate Assurance Calls $ — $ — $ — $ (840 ) $ (2,179 ) Without Adequate Assurance Calls — — — (840 ) (1,910 ) NW Natural's financial derivative instruments are subject to master netting arrangements; however, they are presented on a gross basis in the consolidated balance sheets. NW Natural and its counterparties have the ability to set-off obligations to each other under specified circumstances. Such circumstances may include a defaulting party, a credit change due to a merger affecting either party, or any other termination event. If netted by counterparty, NW Natural's physical and financial derivative position would result in an asset of $1.6 million and a liability of $5.5 million as of June 30, 2019 , an asset of $ 2.5 million and a liability of $ 15.0 million as of June 30, 2018 , and an asset of $3.6 million and a liability of $9.3 million as of December 31, 2018 . NW Natural is exposed to derivative credit and liquidity risk primarily through securing fixed price natural gas commodity swaps to hedge the risk of price increases for natural gas purchases made on behalf of customers. See Note 15 in the 2018 Form 10-K for additional information. Fair Value In accordance with fair value accounting, NW Natural includes non-performance risk in calculating fair value adjustments. This includes a credit risk adjustment based on the credit spreads of NW Natural counterparties when in an unrealized gain position, or on NW Natural's own credit spread when in an unrealized loss position. The inputs in our valuation models include natural gas futures, volatility, credit default swap spreads and interest rates. Additionally, the assessment of non-performance risk is generally derived from the credit default swap market and from bond market credit spreads. The impact of the credit risk adjustments for all outstanding derivatives was immaterial to the fair value calculation at June 30, 2019 . Using significant other observable or Level 2 inputs, the net fair value was a liability of $ 3.9 million , a liability of $ 12.5 million , and a liability of $5.7 million as of June 30, 2019 and 2018 , and December 31, 2018 , respectively. No Level 3 inputs were used in our derivative valuations, and there were no transfers between Level 1 or Level 2 during the six months ended June 30, 2019 and 2018 . See Note 2 in the 2018

Environmental Matters

Environmental Matters	6 Months Ended
	Jun. 30, 2019
Environmental Remediation Obligations [Abstract]
Environmental Matters	ENVIRONMENTAL MATTERS NW Natural owns, or previously owned, properties that may require environmental remediation or action. The range of loss for environmental liabilities is estimated based on current remediation technology, enacted laws and regulations, industry experience gained at similar sites, and an assessment of the probable level of involvement and financial condition of other potentially responsible parties (PRPs). When amounts are prudently expended related to site remediation of those sites described herein, NW Natural has a recovery mechanism in place to collect 96.68% of remediation costs allocable to Oregon customers, and NW Natural is allowed to defer environmental remediation costs allocated to customers in Washington annually until they are reviewed for prudence at a subsequent proceeding. These sites are subject to the remediation process prescribed by the Environmental Protection Agency (EPA) and the Oregon Department of Environmental Quality (ODEQ). The process begins with a remedial investigation (RI) to determine the nature and extent of contamination and then a risk assessment (RA) to establish whether the contamination at the site poses unacceptable risks to humans and the environment. Next, a feasibility study (FS) or an engineering evaluation/cost analysis (EE/CA) evaluates various remedial alternatives. It is at this point in the process when NW Natural is able to estimate a range of remediation costs and record a reasonable potential remediation liability, or make an adjustment to the existing liability. From this study, the regulatory agency selects a remedy and issues a Record of Decision (ROD). After a ROD is issued, NW Natural would seek to negotiate a consent decree or consent judgment for designing and implementing the remedy. NW Natural would have the ability to further refine estimates of remediation liabilities at that time. Remediation may include treatment of contaminated media such as sediment, soil and groundwater, removal and disposal of media, institutional controls such as legal restrictions on future property use, or natural recovery. Following construction of the remedy, the EPA and ODEQ also have requirements for ongoing maintenance, monitoring and other post-remediation care that may continue for many years. Where appropriate and reasonably known, NW Natural will provide for these costs in the remediation liabilities described below. Due to the numerous uncertainties surrounding the course of environmental remediation and the preliminary nature of several site investigations, in some cases, NW Natural may not be able to reasonably estimate the high end of the range of possible loss. In those cases, the nature of the possible loss has been disclosed, as has the fact that the high end of the range cannot be reasonably estimated where a range of potential loss is available. Unless there is an estimate within the range of possible losses that is more likely than other cost estimates within that range, NW Natural records the liability at the low end of this range. It is likely changes in these estimates and ranges will occur throughout the remediation process for each of these sites due to the continued evaluation and clarification concerning responsibility, the complexity of environmental laws and regulations and the determination by regulators of remediation alternatives. In addition to remediation costs, NW Natural could also be subject to Natural Resource Damages (NRD) claims. NW Natural will assess the likelihood and probability of each claim and recognize a liability if deemed appropriate. Refer to " Other Portland Harbor " below. Environmental Sites The following table summarizes information regarding liabilities related to environmental sites, which are recorded in other current liabilities and other noncurrent liabilities in NW Natural's balance sheet: Current Liabilities Non-Current Liabilities June 30, December 31, June 30, December 31, In thousands 2019 2018 2018 2019 2018 2018 Portland Harbor site: Gasco/Siltronic Sediments $ 4,403 $ 2,174 $ 5,117 $ 44,374 $ 45,330 $ 44,351 Other Portland Harbor 2,150 1,444 2,600 5,645 3,871 6,273 Gasco/Siltronic Upland site 9,964 9,947 13,983 42,672 45,578 44,830 Central Service Center site 10 25 10 — — — Front Street site 1,051 906 11,402 10,150 10,683 3 Oregon Steel Mills — — — 179 179 179 Total $ 17,578 $ 14,496 $ 33,112 $ 103,020 $ 105,641 $ 95,636 PORTLAND HARBOR SITE. The Portland Harbor is an EPA listed Superfund site that is approximately 10 miles long on the Willamette River and is adjacent to NW Natural's Gasco uplands site. NW Natural is one of over one hundred PRPs, each jointly and severally liable, to the Superfund site. In January 2017, the EPA issued its Record of Decision, which selects the remedy for the cleanup 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 is actively pursuing clarification and flexibility under the Portland Harbor ROD in order to better understand its obligations. NW Natural's potential liability is a portion of the costs of the remedy for the entire Portland Harbor Superfund site. The cost of that remedy is expected to be allocated among more than 100 PRPs. 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 and, as a result of issuance of the Portland Harbor ROD, NW Natural has not modified any of the recorded liabilities at this time. NW Natural manages the liability related to the Superfund site as two distinct remediation projects: the Gasco/Siltronic Sediments and Other Portland Harbor projects. Gasco/Siltronic Sediments. In 2009, NW Natural and Siltronic Corporation entered into a separate Administrative Order on Consent with the EPA to evaluate and design specific remedies for sediments adjacent to the Gasco uplands and Siltronic uplands sites. NW Natural submitted a draft EE/CA to the EPA in May 2012 to provide the estimated cost of potential remedial alternatives for this site. At this time, the estimated costs for the various sediment remedy alternatives in the draft EE/CA for the additional studies and design work needed before the cleanup can occur, and for regulatory oversight throughout the cleanup range from $48.8 million to $350 million . NW Natural has recorded a liability of $48.8 million for the sediment cleanup, which reflects the low end of the range. At this time, NW Natural believes sediments at this site represent the largest portion of its liability related to the Portland Harbor site discussed above. Other Portland Harbor. While we believe liabilities associated with the Gasco/Siltronic sediments site represent NW Natural's largest exposure, there are other potential exposures associated with the Portland Harbor ROD, including NRD costs and harborwide 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. The Magistrate Judge has recommended granting NW Natural and certain other defendants' motion to stay the case. NW Natural has recorded a liability for NRD claims which is at the low end of the range of the potential liability; the high end of the range cannot be reasonably estimated at this time. The NRD liability is not included in the aforementioned range of costs provided in the Portland Harbor ROD. GASCO UPLANDS SITE. A predecessor of NW Natural, Portland Gas and Coke Company, owned a former gas manufacturing plant that was closed in 1958 (Gasco site) and is adjacent to the Portland Harbor site described above. The Gasco site has been under investigation by NW Natural for environmental contamination under the ODEQ Voluntary 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 the RA, enabling commencement of work on the FS in 2016. NW Natural has recognized a liability for the remediation of the uplands portion of the site which is at the low end of the range of potential liability; the high end of the range cannot be reasonably estimated at this time. In October 2016, ODEQ and NW Natural agreed to amend their VCP agreement to incorporate a portion of the Siltronic property adjacent to the Gasco site formerly owned by Portland Gas & Coke between 1939 and 1960 into the Gasco RA and FS, excluding the uplands for Siltronic. Previously, NW Natural was conducting an investigation of manufactured gas plant constituents on the entire Siltronic uplands for ODEQ. Siltronic will be working with ODEQ directly on environmental impacts to the remainder of its property. In September 2013, NW Natural completed construction of a groundwater source control system, including a water treatment station, at the Gasco site. NW Natural has estimated the cost associated with the ongoing operation of the system and has recognized a liability which is at the low end of the range of potential cost. NW Natural cannot estimate the high end of the range at this time due to the uncertainty associated with the duration of running the water treatment station, which is highly dependent on the remedy determined for both the upland portion as well as the final remedy for Gasco sediment exposure. OTHER SITES. In addition to those sites above, NW Natural has environmental exposures at three other sites: Central Service Center, Front Street and Oregon Steel Mills. NW Natural may have exposure at other sites that have not been identified at this time. Due to the uncertainty of the design of remediation, regulation, timing of the remediation and in the case of the Oregon Steel Mills site, pending litigation, liabilities for each of these sites have been recognized at their respective low end of the range of potential liability; the high end of the range could not be reasonably estimated at this time. Central Service Center site. NW Natural is currently performing an environmental investigation of the property under ODEQ's Independent Cleanup Pathway. This site is on ODEQ's list of sites with confirmed releases of hazardous substances, and cleanup is necessary. Front Street site. The Front Street site was the former location of a gas manufacturing plant NW Natural operated (the former Portland Gas Manufacturing site, or PGM). At ODEQ’s request, NW Natural conducted a sediment and source control investigation and provided findings to ODEQ. In December 2015, an FS on the former Portland Gas Manufacturing site was completed. In July 2017, ODEQ issued the PGM ROD. The ROD specifies the selected remedy, which requires a combination of dredging, capping, treatment, and natural recovery. In addition, the selected remedy also requires institutional controls and long-term inspection and maintenance. NW Natural revised the liability in the second quarter of 2017 to incorporate the estimated undiscounted cost of approximately $10.5 million for the selected remedy. Further, NW Natural has recognized an additional liability of $0.7 million for additional studies and design costs as well as regulatory oversight throughout the cleanup. NW Natural plans to complete the remedial design in 2019 and currently expects to construct the remedy in 2020. Oregon Steel Mills site. Refer to " Legal Proceedings" below. Site Remediation and Recovery Mechanism (SRRM) NW Natural has an SRRM through which it tracks and has the ability to recover past deferred and future prudently incurred environmental remediation costs allocable to Oregon, subject to an earnings test, for those sites identified therein. See Note 17 in the 2018 Form 10-K for a description of the SRRM collection process. The following table presents information regarding the total regulatory asset deferred: June 30, December 31, In thousands 2019 2018 2018 Deferred costs and interest (1) $ 43,222 $ 46,862 $ 41,883 Accrued site liabilities (2) 120,226 119,712 128,369 Insurance proceeds and interest (90,119 ) (95,824 ) (88,502 ) Total regulatory asset deferral (1) $ 73,329 $ 70,750 $ 81,750 Current regulatory assets (3) 5,089 5,594 5,601 Long-term regulatory assets (3) 68,240 65,156 76,149 (1) Includes pre-review and post-review deferred costs, amounts currently in amortization, and interest, net of amounts collected from customers. (2) Excludes 3.32% of the Front Street site liability, or $0.4 million in 2019 and $0.4 million in 2018 , as the OPUC only allows recovery of 96.68% of costs for those sites allocable to Oregon, including those that historically served only Oregon customers. (3) Environmental costs relate to specific sites approved for regulatory deferral by the OPUC and WUTC. In Oregon, NW Natural earns a carrying charge on cash amounts paid, whereas amounts accrued but not yet paid do not earn a carrying charge until expended. It also accrues a carrying charge on insurance proceeds for amounts owed to customers. In Washington, a carrying charge related to deferred amounts is expected to be determined in the current general rate case. Current environmental costs represent remediation costs management expects to collect from customers in the next 12 months. Amounts included in this estimate are still subject to a prudence and earnings test review by the OPUC and do not include the $5.0 million tariff rider. The amounts allocable to Oregon are recoverable through NGD rates, subject to an earnings test. ENVIRONMENTAL EARNINGS TEST. To the extent NW Natural earns at or below its authorized Return on Equity (ROE) as defined by the SRRM, remediation expenses and interest in excess of the $5.0 million tariff rider and $5.0 million insurance proceeds are recoverable through the SRRM. To the extent that NW Natural earns more than its authorized ROE in a year, it is required to cover environmental expenses and interest on expenses greater than the $10.0 million with those earnings that exceed its authorized ROE. In the first quarter of 2019, NW Natural recorded a $4.4 million reserve for an anticipated adjustment for fiscal year 2019 as a result of expected earnings that would exceed the authorized ROE and expenses that would be subject to deferral through the SRRM. In the second quarter of 2019, compliance with certain remediation requirements delayed an environmental project to 2020 and accordingly the reserve was reversed for the change in amounts that would be subject to deferral through the SRRM. Under the 2015 Order, the OPUC stated they would revisit the deferral and amortization of future remediation expenses, as well as the treatment of remaining insurance proceeds three years from the original Order, or earlier if NW Natural gains greater certainty about future remediation costs, to consider whether adjustments to the mechanism may be appropriate. NW Natural filed an update with the OPUC in March 2018 and recommended no changes. WASHINGTON DEFERRAL. Cost recovery and carrying charges on amounts deferred for costs associated with services provided to Washington customers will be determined in a future proceeding. Legal Proceedings Other than the matters discussed above, NW Holdings is not currently party to any direct claims or litigation, though in the future it may be subject to claims and litigation arising in the ordinary course of business. NW Natural is subject to claims and litigation arising in the ordinary course of business. Although the final outcome of any of these legal proceedings cannot be predicted with certainty, including the matter described below, NW Natural and NW Holdings do not expect that the ultimate disposition of any of these matters will have a material effect on financial condition, results of operations or cash flows. See also Part II, Item 1, “ Legal Proceedings" . OREGON STEEL MILLS SITE. See Note 17 in the 2018 Form 10-K. For additional information regarding other commitments and contingencies, see Note 16 in the 2018 Form 10-K.

Discontinued Operations

Discontinued Operations	6 Months Ended
	Jun. 30, 2019
Discontinued Operations and Disposal Groups [Abstract]
Discontinued Operations	DISCONTINUED OPERATIONS NW Holdings On June 20, 2018, NWN Gas Storage, then a wholly owned subsidiary of NW Natural, entered into a Purchase and Sale Agreement (the Agreement) that provides for the sale by NWN Gas Storage of all of the membership interests in Gill Ranch. Gill Ranch owns a 75% interest in the natural gas storage facility located near Fresno, California known as the Gill Ranch Gas Storage Facility. Pacific Gas and Electric Company (PG&E) owns the remaining 25% interest in the Gill Ranch Gas Storage Facility. The CPUC regulates Gill Ranch under a market-based rate model which allows for the price of storage services to be set by the marketplace. The CPUC also regulates the issuance of securities, system of accounts, and regulates intrastate storage services. The Agreement provides for an initial cash purchase price of $25.0 million (subject to a working capital adjustment), plus potential additional payments to NWN Gas Storage of up to $26.5 million in the aggregate if Gill Ranch achieves certain economic performance levels for the first three full gas storage years (April 1 of one year through March 31 of the following year) occurring after the closing and the remaining portion of the gas storage year during which the closing occurs. The closing of the transaction is subject to approval by the CPUC and other customary closing conditions. In July 2018, Gill Ranch filed an application with the CPUC for approval of this transaction. On February 14, 2019, the active parties to the CPUC proceeding filed a settlement agreement with the CPUC. On July 23, 2019, one of the parties to the settlement agreement, the CPUC’s Office of Safety Advocates (OSA), filed a motion with the CPUC to withdraw from the settlement agreement and requested a new pre-hearing conference. On July 29, 2019, Gill Ranch and the proposed purchaser filed motions with the CPUC to strike the OSA’s motion of withdrawal together with a request to supplement the evidentiary record with materials which the applicants believe demonstrate that the issues raised by the OSA are not relevant to the CPUC proceeding. We continue to strive to close this transaction by the end of 2019. As a result of the strategic shift away from the California gas storage market and the significance of Gill Ranch's financial results in 2017, we concluded that the pending sale of Gill Ranch qualified it as assets and liabilities held for sale and discontinued operations. As such, the assets and liabilities associated with Gill Ranch have been classified as discontinued operations assets and discontinued operations liabilities, respectively, and, the results of Gill Ranch are presented, net of tax, as discontinued operations separately from the results of continuing operations for all periods presented. The expenses included in the results of discontinued operations are the direct operating expenses incurred by Gill Ranch that may be reasonably segregated from the costs of NW Holdings' continuing operations. The following table presents the carrying amounts of the major components of Gill Ranch that are classified as discontinued operations assets and liabilities on the consolidated balance sheets: NW Holdings Discontinued Operations June 30, December 31, In thousands 2019 2018 2018 Assets: Accounts receivable $ 519 $ 497 $ 390 Inventories 756 646 685 Other current assets 183 413 333 Property, plant, and equipment 12,184 10,948 11,621 Less: Accumulated depreciation 6 6 7 Operating lease right of use asset 118 — — Other non-current assets 247 245 247 Total discontinued operations assets - current assets (1) $ 14,001 $ 12,743 $ 13,269 Liabilities: Accounts payable $ 1,230 $ 572 $ 873 Other current liabilities 296 436 307 Operating lease liabilities 113 — — Other non-current liabilities 11,640 11,914 11,779 Total discontinued operations liabilities - current liabilities (1) $ 13,279 $ 12,922 $ 12,959 (1) The total assets and liabilities of Gill Ranch are classified as current as of June 30, 2019 and December 31, 2018 because it is probable that the sale will be completed within one year. The following table presents the operating results of Gill Ranch, which was reported within the gas storage segment historically, and is presented net of tax on the consolidated statements of comprehensive income: NW Holdings Discontinued Operations Three Months Ended June 30, Six Months Ended June 30, In thousands, except per share data 2019 2018 2019 2018 Revenues $ 1,748 $ 1,006 $ 3,469 $ 2,083 Expenses: Operations and maintenance 2,651 1,554 4,264 2,590 General taxes 60 346 119 680 Depreciation and amortization 106 108 212 218 Other expenses and interest 229 (107 ) 466 134 Total expenses 3,046 1,901 5,061 3,622 Loss from discontinued operations before income taxes (1,298 ) (895 ) (1,592 ) (1,539 ) Income tax benefit (342 ) (236 ) (419 ) (406 ) Loss from discontinued operations, net of tax $ (956 ) $ (659 ) $ (1,173 ) $ (1,133 ) Loss from discontinued operations per share of common stock: Basic $ (0.03 ) $ (0.02 ) $ (0.04 ) $ (0.04 ) Diluted $ (0.03 ) $ (0.02 ) $ (0.04 ) $ (0.04 ) NW Natural As a result of the holding company reorganization in October 2018, NWN Energy, NWN Gas Storage, Gill Ranch, NNG Financial, NWN Water, and NW Holdings, which were direct and indirect subsidiaries of NW Natural prior to the reorganization, are no longer subsidiaries of NW Natural. As a result, NW Natural's financial statements reflect amounts related to these entities as discontinued operations for all periods presented. The expenses included in the results of discontinued operations are the direct operating expenses incurred by the entities that may be reasonably segregated from the costs of NW Natural's continuing operations. The following table presents the carrying amounts of the major components of NWN Energy, NWN Gas Storage, Gill Ranch, NNG Financial, NWN Water, and NW Holdings that are classified as discontinued operations assets and liabilities on NW Natural's consolidated balance sheets: NW Natural Discontinued Operations In thousands June 30, 2018 Assets: Cash $ 433 Accounts receivable 498 Receivables from affiliates 3,814 Inventories 646 Other current assets 482 Property, plant, and equipment 11,323 Less: Accumulated depreciation 213 Other investments 13,673 Other non-current assets 254 Discontinued operations - current assets 5,873 Discontinued operations - non-current assets 25,037 Total discontinued operations assets $ 30,910 Liabilities: Accounts payable $ 971 Taxes accrued 30 Payables to affiliates 265 Other current liabilities 1,436 Deferred tax liabilities (15,022 ) Other non-current liabilities 12,004 Discontinued operations - current liabilities 2,702 Discontinued operations - non-current liabilities (3,018 ) Total discontinued operations liabilities $ (316 ) The following table presents the operating results prior to the holding company reorganization effective October 1, 2018 of NWN Energy, NWN Gas Storage, Gill Ranch, NNG Financial, NWN Water, and NW Holdings, which were historically reported within the gas storage segment and other, and is presented net of tax on NW Natural's consolidated statements of comprehensive income: NW Natural Three Months Ended June 30, Six Months Ended June 30, In thousands, except per share data 2018 2018 Revenues $ 1,065 $ 2,198 Expenses: Operations and maintenance 1,684 2,743 General taxes 356 703 Depreciation and amortization 165 282 Other expenses and interest (150 ) 110 Total expenses 2,055 3,838 Loss from discontinued operations before income taxes (990 ) (1,640 ) Income tax benefit (263 ) (436 ) Loss from discontinued operations, net of tax $ (727 ) $ (1,204 )

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Industry Regulation	Industry Regulation In applying regulatory accounting principles, NW Holdings and NW Natural capitalize or defer certain costs and revenues as regulatory assets and liabilities pursuant to orders of the Oregon Public Utilities Commission (OPUC), Washington Utilities and Transportation Commission (WUTC) or Idaho Public Utilities Commission (IPUC), which provide for the recovery of revenues or expenses from, or refunds to, utility customers in future periods, including a return or a carrying charge in certain cases.
New Accounting Standards	New Accounting Standards We consider the applicability and impact of all accounting standards updates (ASUs) issued by the Financial Accounting Standards Board (FASB). ASUs not listed below were assessed and determined to be either not applicable or are expected to have minimal impact on NW Natural's consolidated financial position or results of operations. Recently Adopted Accounting Pronouncements ACCUMULATED OTHER COMPREHENSIVE INCOME. On February 14, 2018, the FASB issued ASU 2018-02, "Income Statement—Reporting Comprehensive Income: Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income." This update was issued in response to concerns from certain stakeholders regarding the current requirements under U.S. GAAP that deferred tax assets and liabilities are adjusted for a change in tax laws or rates, and the effect is to be included in income from continuing operations in the period of the enactment date. This requirement is also applicable to items in accumulated other comprehensive income where the related tax effects were originally recognized in other comprehensive income. The adjustment of deferred taxes due to the new corporate income tax rate enacted through the Tax Cuts and Jobs Act (TCJA) on December 22, 2017 recognized in income from continuing operations causes the tax effects of items within accumulated other comprehensive income (referred to as stranded tax effects) to not reflect the appropriate tax rate. The amendments in this update allow but do not require a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the TCJA and require certain disclosures about stranded tax effects. NW Natural adopted and applied the standard in the first quarter of 2019. NW Natural elected to reclassify the stranded tax effects of the TJCA of $1.4 million from accumulated other comprehensive loss to retained earnings in the period of adoption. Going forward, our policy is that, in the event that regulation changes result in stranded tax effects, such amounts will be reclassified from accumulated other comprehensive income (loss) to retained earnings in the final period that the related deferred tax balance remeasurement is expected to impact income from continuing operations. DERIVATIVES AND HEDGING. On August 28, 2017, the FASB issued ASU 2017-12, "Derivatives and Hedging: Targeted Improvements to Accounting for Hedging Activities." The purpose of the amendment is to more closely align hedge accounting with companies’ risk management strategies. The ASU amends the accounting for risk component hedging, the hedged item in fair value hedges of interest rate risk, and amounts excluded from the assessment of hedge effectiveness. The guidance also amends the recognition and presentation of the effect of hedging instruments and includes other simplifications of hedge accounting. The amendments in this update were effective beginning January 1, 2019 and were applied prospectively to hedging instruments. The adoption did not have an impact on the financial statements or disclosures of NW Holdings or NW Natural. GOODWILL. On January 26, 2017, the FASB issued ASU 2017-04, "Simplifying the Test for Goodwill Impairment." The ASU removes Step 2 from the goodwill impairment test and under the amended guidance an entity should perform its annual goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount and recognize an impairment charge for the amount in which the carrying amounts exceed the fair value of the reporting unit. The amendments in this standard are effective for us beginning January 1, 2020 and early adoption is permitted for interim or annual goodwill impairment tests performed after January 1, 2017. NW Natural early adopted ASU 2017-04 in the quarter ended September 30, 2018. The adoption of this ASU did not materially affect the financial statements and disclosures of NW Holdings or NW Natural. LEASES. On February 25, 2016, the FASB issued ASU 2016-02, "Leases," which revises the existing lease accounting guidance. Pursuant to the new standard (“ASC 842”), lessees are required to recognize all leases, including operating leases that are greater than 12 months at lease commencement, on the balance sheet and record corresponding right of use assets and lease liabilities. Lessor accounting will remain substantially the same under the new standard. Quantitative and qualitative disclosures are also required for users of the financial statements to have a clear understanding of the nature of our leasing activities. We elected the alternative prospective transition approach for adoption beginning January 1, 2019. All comparative periods prior to January 1, 2019 will retain the financial reporting and disclosure requirements of ASC 840 “Leases” (“ASC 840”). There was no cumulative effect adjustment to the opening balance of retained earnings recorded as of January 1, 2019 for adoption as there were no initial direct costs or other capitalized costs related to the legacy leases that needed to be derecognized upon adoption of ASC 842. We elected the land easement optional practical expedient to not evaluate existing or expired land easements that were not previously accounted for as leases under the ASC 840 lease guidance. For the existing lease portfolio, we did not elect the optional practical expedient package to retain the legacy lease accounting conclusions upon adoption; we re-assessed our existing contracts under the new leasing standard including whether the contract meets the definition of a lease and lease classification. As a result, we determined that most of our underground gas storage contracts no longer meet the definition of a lease under the new lease standard. Our lease portfolio under the new standard consists primarily of our current leased headquarters, which expires in 2020. In October 2017, NW Natural entered into a 20-year operating lease agreement commencing in 2020 for a new headquarters location in Portland, Oregon. The lease was analyzed under ASC 840 in consideration of build-to-suit lease accounting guidance with the conclusion that NW Natural was the owner of the asset during construction for accounting purposes. Under the new lease standard, ASC 842, NW Natural is no longer considered the owner of the asset during construction for accounting purposes. As such, in January 2019 we derecognized the build-to-suit asset and liability balances of $26.0 million as of December 31, 2018 that were previously recorded within property, plant and equipment and other non-current liabilities in the consolidated balance sheet. Upon adoption on January 1, 2019, NW Holdings recorded an operating lease right of use asset and an associated operating lease liability of approximately $7.3 million , of which $7.0 million was recorded at NW Natural. Lease liabilities are measured using NW Natural's incremental borrowing rate based on information available at the lease commencement date in determining the present value of lease payments. See Note 7 . CLOUD COMPUTING. On August 29, 2018, the FASB issued ASU 2018-15, "Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract." The purpose of the amendment is to align the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. The amendments in this update are effective for us beginning January 1, 2020. Early adoption is permitted, and NW Holdings and NW Natural early adopted ASU 2018-15 in the quarter ended March 31, 2019 utilizing the prospective application methodology. The adoption of this ASU did not materially affect the financial statements and disclosures of NW Holdings or NW Natural. Recently Issued Accounting Pronouncements RETIREMENT BENEFITS. On August 28, 2018, the FASB issued ASU 2018-14, "Changes to the Disclosure Requirements for Defined Benefit Plans." The purpose of the amendment is to modify the disclosure requirements for defined benefit pension and other postretirement plans. The amendments in this update are effective for us beginning January 1, 2020. Early adoption is permitted. The amended presentation and disclosure guidance should be applied retrospectively. We are currently assessing the effect of this standard on disclosures. FAIR VALUE MEASUREMENT. On August 28, 2018, the FASB issued ASU 2018-13, "Changes to the Disclosure Requirements for Fair Value Measurement." The purpose of the amendment is to modify the disclosure requirements for fair value measurements. The amendments in this update are effective for us beginning January 1, 2020. Early adoption is permitted. The amendments on changes in unrealized gains and losses, the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements and the narrative description of measurement uncertainty should be applied prospectively. All other amendments should be applied retrospectively. We are currently assessing the effect of this standard on disclosures. CREDIT LOSSES. On June 16, 2016, the FASB issued ASU 2016-13, "Measurement of Credit Losses on Financial Instruments," which applies to financial assets subject to credit losses and measured at amortized cost. The new standard will require financial assets measured at amortized cost to be presented at the net amount expected to be collected and the allowance for credit losses is to be recorded as a valuation account that is deducted from the amortized cost basis. The amendments in this update are effective beginning January 1, 2020. Early adoption is permitted for fiscal years beginning after December 15, 2018. We are currently assessing the effect of this standard, and subsequent standard updates which clarify ASU 2016-13, on our financial statements and disclosures.

Significant Accounting Polici_3

Significant Accounting Policies (Tables)	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Schedule of Regulatory Assets	Amounts deferred as regulatory assets and liabilities were as follows: Regulatory Assets June 30, December 31, In thousands 2019 2018 2018 Current: Unrealized loss on derivatives (1) $ 4,385 $ 11,744 $ 12,381 Gas costs 19,195 273 2,873 Environmental costs (2) 5,089 5,594 5,601 Decoupling (3) 1,680 10,232 9,140 Pension balancing (4) 5,009 — — Income taxes 2,209 2,217 2,218 Other (5) 9,121 11,032 9,717 Total current $ 46,688 $ 41,092 $ 41,930 Non-current: Unrealized loss on derivatives (1) $ 2,062 $ 3,913 $ 3,025 Pension balancing (4) 50,080 67,527 74,173 Income taxes 17,758 19,267 19,185 Pension and other postretirement benefit liabilities 168,137 171,186 174,993 Environmental costs (2) 68,240 65,156 76,149 Gas costs 2,994 28 9,978 Decoupling (3) 37 1,636 2,545 Other (5) 9,032 10,464 11,738 Total non-current $ 318,340 $ 339,177 $ 371,786
Schedule of Regulatory Liabilities	Regulatory Liabilities June 30, December 31, In thousands 2019 2018 2018 Current: Gas costs $ 5,630 $ 20,906 $ 17,182 Unrealized gain on derivatives (1) 1,944 1,938 8,740 Decoupling (3) 857 2,153 2,264 Income taxes 7,763 — — Other (5) 16,290 9,278 19,250 Total current $ 32,484 $ 34,275 $ 47,436 Non-current: Gas costs $ 226 $ 3,460 $ 552 Unrealized gain on derivatives (1) 670 1,077 725 Decoupling (3) 74 410 — Income taxes (6) 202,422 222,734 225,408 Accrued asset removal costs (7) 390,345 370,245 380,464 Other (5) 11,299 4,368 4,411 Total non-current $ 605,036 $ 602,294 $ 611,560 (1) Unrealized gains or losses on derivatives are non-cash items and therefore do not earn a rate of return or a carrying charge. These amounts are recoverable through NGD rates as part of the annual Purchased Gas Adjustment (PGA) mechanism when realized at settlement. (2) Refer to footnote (3) of the Deferred Regulatory Asset table in Note 17 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 10 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 11 . (7) Estimated costs of removal on certain regulated properties are collected through rates.

Earnings Per Share (Tables)

Earnings Per Share (Tables)	6 Months Ended
	Jun. 30, 2019
Earnings Per Share [Abstract]
EPS Calculation	NW Holdings' diluted earnings or loss per share are calculated as follows: Three Months Ended June 30, Six Months Ended June 30, In thousands, except per share data 2019 2018 2019 2018 Net Income (loss) from continuing operations $ 2,051 $ (339 ) $ 45,469 $ 41,672 Loss from discontinued operations, net of tax (956 ) (659 ) (1,173 ) (1,133 ) Net income (loss) $ 1,095 $ (998 ) $ 44,296 $ 40,539 Average common shares outstanding - basic 29,337 28,791 29,123 28,772 Additional shares for stock-based compensation plans (See Note 8) 57 — 63 53 Average common shares outstanding - diluted 29,394 28,791 29,186 28,825 Earnings (loss) from continuing operations per share of common stock: Basic $ 0.07 $ (0.01 ) $ 1.56 $ 1.45 Diluted $ 0.07 $ (0.01 ) $ 1.56 $ 1.45 Loss from discontinued operations per share of common stock: Basic $ (0.03 ) $ (0.02 ) $ (0.04 ) $ (0.04 ) Diluted $ (0.03 ) $ (0.02 ) $ (0.04 ) $ (0.04 ) Earnings (loss) per share of common stock: Basic $ 0.04 $ (0.03 ) $ 1.52 $ 1.41 Diluted $ 0.04 $ (0.03 ) $ 1.52 $ 1.41 Additional information: Anti-dilutive shares 1 53 2 10

Segment Information (Tables)

Segment Information (Tables)	6 Months Ended
	Jun. 30, 2019
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, by Segment	The following table presents summary financial information concerning the reportable segments of continuing operations. See Note 18 for information regarding discontinued operations for NW Holdings and NW Natural. Three Months Ended June 30, In thousands NGD Other (NW Natural) NW Natural Other (NW Holdings) NW Holdings 2019 Operating revenues $ 117,984 $ 4,258 $ 122,242 $ 1,201 $ 123,443 Depreciation and amortization 21,992 251 22,243 144 22,387 Income (loss) from operations 14,657 2,583 17,240 (1,142 ) 16,098 Net income (loss) from continuing operations 1,212 1,842 3,054 (1,003 ) 2,051 Capital expenditures 41,912 105 42,017 366 42,383 2018 Operating revenues $ 118,515 $ 6,048 $ 124,563 $ 4 $ 124,567 Depreciation and amortization 20,766 324 21,090 57 21,147 Income (loss) from operations 4,545 3,860 8,405 (136 ) 8,269 Net income (loss) from continuing operations (2,970 ) 2,699 (271 ) (68 ) (339 ) Capital expenditures 43,801 1,240 45,041 — 45,041 Six Months Ended June 30, In thousands NGD Other (NW Natural) NW Natural Other (NW Holdings) NW Holdings 2019 Operating revenues $ 397,025 $ 10,063 $ 407,088 $ 1,703 $ 408,791 Depreciation and amortization 43,241 506 43,747 212 43,959 Income (loss) from operations 87,555 6,329 93,884 (1,741 ) 92,143 Net income (loss) from continuing operations 42,418 4,531 46,949 (1,480 ) 45,469 Capital expenditures 90,518 157 90,675 472 91,147 Total assets at June 30, 2019 (1) 3,089,944 48,749 3,138,693 85,437 3,224,130 2018 Operating revenues $ 376,448 $ 11,750 $ 388,198 $ 4 $ 388,202 Depreciation and amortization 41,309 649 41,958 64 42,022 Income from operations 69,301 6,842 76,143 (123 ) 76,020 Net income (loss) from continuing operations 36,913 4,830 41,743 (71 ) 41,672 Capital expenditures 100,695 1,675 102,370 — 102,370 Total assets at June 30, 2018 (1) 2,907,936 51,993 2,959,929 14,088 2,974,017 Total assets at December 31, 2018 (1) 3,141,969 50,767 3,192,736 36,657 3,229,393 (1) Total assets for NW Holdings exclude assets related to discontinued operations of $14.0 million , $12.7 million , and $13.3 million as of June 30, 2019 , June 30, 2018 , and December 31, 2018 , respectively. Total assets for NW Natural exclude assets related to discontinued operations of $30.9 million as of June 30, 2018 .
NGD Margin	The following table presents additional segment information concerning NGD margin: Three Months Ended June 30, Six Months Ended June 30, In thousands 2019 2018 2019 2018 NGD margin calculation: NGD distribution revenues $ 115,792 $ 118,435 $ 394,775 $ 376,341 Other regulated services 2,192 80 2,250 107 Total NGD operating revenues 117,984 118,515 397,025 376,448 Less: NGD cost of gas 35,163 42,107 140,676 150,271 Environmental remediation (2,656 ) 1,882 6,291 6,506 Revenue taxes 4,496 4,780 16,422 17,209 NGD margin $ 80,981 $ 69,746 $ 233,636 $ 202,462

Leases (Tables)

Leases (Tables)	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Leases [Abstract]
Lease Revenue	The components of lease revenue at NW Natural were as follows: In thousands Three months ended June 30, 2019 Six months ended June 30, 2019 Lease revenue Operating leases $ 47 $ 95 Sales-type leases 2,085 2,145 Total lease revenue $ 2,132 $ 2,240
Lessor, Operating Lease, Payments to be Received, Maturity	Total future minimum lease payments to be received under non-cancelable leases at NW Natural at June 30, 2019 are as follows: In thousands Operating Sales-Type Total Remainder of 2019 $ 58 $ 9,708 $ 9,766 2020 61 18,228 18,289 2021 49 17,518 17,567 2022 45 17,026 17,071 2023 45 16,557 16,602 Thereafter 138 280,607 280,745 Total lease revenue $ 396 $ 359,644 $ 360,040 Less: imputed interest 208,877 Total leases receivable $ 150,767
Lease Expense	The components of lease expense, a portion of which is capitalized, were as follows: Three months ended June 30, 2019 In thousands NW Natural Other NW Holdings Operating lease expense $ 1,155 $ 46 $ 1,201 Short-term lease expense 331 — 331 Six months ended June 30, 2019 In thousands NW Natural Other NW Holdings Operating lease expense $ 2,297 $ 92 $ 2,389 Short-term lease expense 491 — 491
Operating Lease, Lease Asset and Liabilities	Supplemental balance sheet information related to operating leases as of June 30, 2019 is as follows: In thousands NW Natural Other NW Holdings Operating lease right of use asset $ 4,797 $ 216 $ 5,013 Operating lease liabilities - current liabilities $ 4,141 $ 130 $ 4,271 Operating lease liabilities - non-current liabilities 634 87 721 Total operating lease liabilities $ 4,775 $ 217 $ 4,992
Lessee, Operating Lease, Liability, Maturity	Maturities of operating lease liabilities at June 30, 2019 were as follows: In thousands NW Natural Other NW Holdings Remainder of 2019 $ 2,298 $ 93 $ 2,391 2020 1,980 102 2,082 2021 101 28 129 2022 93 — 93 2023 71 — 71 Thereafter 497 — 497 Total lease payments 5,040 223 5,263 Less: imputed interest 265 6 271 Total lease obligations 4,775 217 4,992 Less: current obligations 4,141 130 4,271 Long-term lease obligations $ 634 $ 87 $ 721	The following table reflects NW Natural's future minimum lease payments due under non-cancelable operating leases for continuing operations at December 31, 2018 . These commitments relate principally to the lease of the office headquarters and underground gas storage facilities. In thousands Minimum lease payments 2019 $ 5,368 2020 4,812 2021 7,077 2022 7,223 2023 7,304 Thereafter 149,881 Total $ 181,665
Lessee, Leases, Supplemental Cash Flow Information	Supplemental cash flow information related to leases was as follows: Three months ended June 30, 2019 In thousands NW Natural Other NW Holdings Cash paid for amounts included in the measurement of lease liabilities Operating cash flows from operating leases $ 1,115 $ 44 $ 1,159 Six months ended June 30, 2019 NW Natural Other NW Holdings Cash paid for amounts included in the measurement of lease liabilities Operating cash flows from operating leases $ 2,206 $ 87 $ 2,293 Right of use assets obtained in exchange for lease obligations Operating leases $ 6,987 $ 304 $ 7,291

Revenue (Tables)

Revenue (Tables)	6 Months Ended
	Jun. 30, 2019
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	The following tables present disaggregated revenue from continuing operations: Three Months Ended June 30, In thousands NGD Other (NW Natural) NW Natural Other (NW Holdings) NW Holdings 2019 Natural gas sales $ 112,015 $ — $ 112,015 $ — $ 112,015 Gas storage revenue, net — 2,740 2,740 — 2,740 Asset management revenue, net — 460 460 — 460 Appliance retail center revenue — 1,058 1,058 — 1,058 Other revenue 104 — 104 1,201 1,305 Revenue from contracts with customers 112,119 4,258 116,377 1,201 117,578 Alternative revenue 3,733 — 3,733 — 3,733 Leasing revenue 2,132 — 2,132 — 2,132 Total operating revenues $ 117,984 $ 4,258 $ 122,242 $ 1,201 $ 123,443 2018 Natural gas sales $ 114,726 $ — $ 114,726 $ — $ 114,726 Gas storage revenue, net — 2,737 2,737 — 2,737 Asset management revenue, net — 2,140 2,140 — 2,140 Appliance retail center revenue — 1,171 1,171 — 1,171 Other revenue — — — 4 4 Revenue from contracts with customers 114,726 6,048 120,774 4 120,778 Alternative revenue 3,663 — 3,663 — 3,663 Leasing revenue 126 — 126 — 126 Total operating revenues $ 118,515 $ 6,048 $ 124,563 $ 4 $ 124,567 Six Months Ended June 30, In thousands NGD Other (NW Natural) NW Natural Other (NW Holdings) NW Holdings 2019 Natural gas sales $ 408,201 $ — $ 408,201 $ — $ 408,201 Gas storage revenue, net — 5,523 5,523 — 5,523 Asset management revenue, net — 1,966 1,966 — 1,966 Appliance retail center revenue — 2,574 2,574 — 2,574 Other revenue 104 — 104 1,703 1,807 Revenue from contracts with customers 408,305 10,063 418,368 1,703 420,071 Alternative revenue (13,520 ) — (13,520 ) — (13,520 ) Leasing revenue 2,240 — 2,240 — 2,240 Total operating revenues $ 397,025 $ 10,063 $ 407,088 $ 1,703 $ 408,791 2018 Natural gas sales $ 372,954 $ — $ 372,954 $ — $ 372,954 Gas storage revenue, net — 5,314 5,314 — 5,314 Asset management revenue, net — 3,719 3,719 — 3,719 Appliance retail center revenue — 2,717 2,717 — 2,717 Other revenue — — — 4 4 Revenue from contracts with customers 372,954 11,750 384,704 4 384,708 Alternative revenue 3,291 — 3,291 — 3,291 Leasing revenue 203 — 203 — 203 Total operating revenues $ 376,448 $ 11,750 $ 388,198 $ 4 $ 388,202

Debt (Tables)

Debt (Tables)	6 Months Ended
	Jun. 30, 2019
Debt Disclosure [Abstract]
Schedule of Carrying Values and Estimated Fair Values of Debt Instruments	The following table provides an estimate of the fair value of NW Holdings' long-term debt, including current maturities of long-term debt, using market prices in effect on the valuation date: NW Holdings June 30, December 31, In thousands 2019 2018 2018 Gross long-term debt $ 916,832 $ 764,700 $ 741,813 Unamortized debt issuance costs (6,435 ) (6,020 ) (5,577 ) Carrying amount $ 910,397 $ 758,680 $ 736,236 Estimated fair value (1) $ 970,205 $ 792,623 $ 762,335 (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 June 30, December 31, In thousands 2019 2018 2018 Gross long-term debt $ 879,700 $ 764,700 $ 739,700 Unamortized debt issuance costs (6,394 ) (6,020 ) (5,577 ) Carrying amount $ 873,306 $ 758,680 $ 734,123 Estimated fair value (1) $ 933,167 $ 792,623 $ 760,222 (1) Estimated fair value does not include unamortized debt issuance costs.

Pension and Other Postretirem_2

Pension and Other Postretirement Benefit Costs (Tables)	6 Months Ended
	Jun. 30, 2019
Pension and Other Postretirement Benefits Cost (Reversal of Cost) [Abstract]
Schedule of Net Benefit Costs	The following table provides the components of net periodic benefit cost for the pension and other postretirement benefit plans: Three Months Ended June 30, Six Months Ended June 30, Pension Benefits Other Postretirement Benefits Pension Benefits Other Postretirement Benefits In thousands 2019 2018 2019 2018 2019 2018 2019 2018 Service cost $ 1,516 $ 1,807 $ 67 $ 79 $ 3,033 $ 3,614 $ 135 $ 159 Interest cost 4,661 4,183 283 241 9,323 8,366 564 482 Expected return on plan assets (5,207 ) (5,150 ) — — (10,414 ) (10,301 ) — — Amortization of prior service costs 2 10 (117 ) (117 ) 4 21 (234 ) (234 ) Amortization of net actuarial loss 3,603 4,524 96 112 7,206 9,047 193 222 Net periodic benefit cost 4,575 5,374 329 315 9,152 10,747 658 629 Amount allocated to construction (596 ) (685 ) (23 ) (28 ) (1,182 ) (1,367 ) (47 ) (55 ) Amount deferred to regulatory balancing account — (2,747 ) — — — (5,503 ) — — Net periodic benefit cost charged to expense 3,979 1,942 306 287 7,970 3,877 611 574 Regulatory pension disallowance — — — — 10,500 — — — Amortization of regulatory balancing account 1,281 — — — 13,792 — — — Net amount charged to expense $ 5,260 $ 1,942 $ 306 $ 287 $ 32,262 $ 3,877 $ 611 $ 574
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 June 30, Six Months Ended June 30, In thousands 2019 2018 2019 2018 Beginning balance $ (8,439 ) $ (8,284 ) $ (7,188 ) $ (8,438 ) Amounts reclassified from AOCL: Amortization of actuarial losses 156 209 312 418 Reclassification of stranded tax effects (1) — — (1,366 ) — Total reclassifications before tax 156 209 (1,054 ) 418 Tax (benefit) expense (41 ) (56 ) (82 ) (111 ) Total reclassifications for the period 115 153 (1,136 ) 307 Ending balance $ (8,324 ) $ (8,131 ) $ (8,324 ) $ (8,131 ) (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)	6 Months Ended
	Jun. 30, 2019
Income Tax Disclosure [Abstract]
Schedule of Effective Income Tax Rate Reconciliation	The effective income tax rate varied from the combined federal and state statutory tax rates due to the following: Three Months Ended June 30, NW Holdings NW Natural In thousands 2019 2018 2019 2018 Income taxes at statutory rates (federal and state) $ 694 $ (135 ) $ 1,055 $ (107 ) Increase (decrease): Differences required to be flowed-through by regulatory commissions (37 ) (14 ) (37 ) (14 ) Other, net (32 ) (7 ) (33 ) (7 ) Total provision for income taxes on continuing operations $ 625 $ (156 ) $ 985 $ (128 ) Effective tax rate for continuing operations 23.4 % 31.5 % 24.4 % 32.1 % Six Months Ended June 30, NW Holdings NW Natural In thousands 2019 2018 2019 2018 Income taxes at statutory rates (federal and state) $ 15,007 $ 15,233 $ 15,540 $ 15,264 Increase (decrease): Differences required to be flowed-through by regulatory commissions (5,297 ) 835 (5,297 ) 835 Other, net (410 ) (592 ) (410 ) (592 ) Total provision for income taxes on continuing operations $ 9,300 $ 15,476 $ 9,833 $ 15,507 Effective tax rate for continuing operations 17.0 % 27.1 % 17.3 % 27.1 %

Property, Plant and Equipment_2

Property, Plant and Equipment (Tables)	6 Months Ended
	Jun. 30, 2019
Property, Plant and Equipment [Abstract]
Public Utility Property, Plant, and Equipment [Table Text Block]	The following table sets forth the major classifications of property, plant, and equipment and accumulated depreciation of continuing operations: June 30, December 31, In thousands 2019 2018 2018 NW Natural: NGD plant in service $ 3,193,121 $ 3,035,089 $ 3,134,122 NGD work in progress 75,045 192,496 204,978 Less: Accumulated depreciation 997,111 966,766 974,252 NGD plant, net 2,271,055 2,260,819 2,364,848 Other plant in service 63,385 65,548 66,009 Other construction work in progress 5,454 5,347 5,330 Less: Accumulated depreciation 18,650 18,024 18,603 Other plant, net (1) 50,189 52,871 52,736 Total property, plant, and equipment $ 2,321,244 $ 2,313,690 $ 2,417,584 Other (NW Holdings): Other plant in service $ 18,806 $ 376 $ 4,051 Less: Accumulated depreciation 424 208 263 Other plant, net (1) $ 18,382 $ 168 $ 3,788 NW Holdings: Total property, plant, and equipment $ 2,339,626 $ 2,313,858 $ 2,421,372 NW Natural and NW Holdings: Capital expenditures in accrued liabilities $ 32,923 $ 22,112 $ 23,676 (1) NW Natural p reviously reported other balances were restated due to certain assets and liabilities now being classified as discontinued operations assets and liabilities in its balance sheets. See Note 18 for further discussion.

Gas Reserves (Tables)

Gas Reserves (Tables)	6 Months Ended
	Jun. 30, 2019
Gas Reserves [Abstract]
Gas Reserves	The following table outlines NW Natural's net gas reserves investment: June 30, December 31, In thousands 2019 2018 2018 Gas reserves, current $ 17,206 $ 16,579 $ 16,647 Gas reserves, non-current 170,101 170,958 170,660 Less: Accumulated amortization 113,930 95,596 104,463 Total gas reserves (1) 73,377 91,941 82,844 Less: Deferred taxes on gas reserves 26,995 20,381 20,071 Net investment in gas reserves $ 46,382 $ 71,560 $ 62,773 (1) The net investment in additional wells included in total gas reserves was $ 4.3 million , $ 5.5 million and $ 4.8 million at June 30, 2019 and 2018 and December 31, 2018

Business Combinations Busines_2

Business Combinations Business Combinations (Tables)	6 Months Ended
	Jun. 30, 2019
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 assets acquired as of the acquisition date and is as follows: In thousands May 31, 2019 Current assets $ 211 Property, plant and equipment 14,009 Goodwill 40,153 Deferred tax assets 828 Total assets acquired $ 55,201

Derivative Instruments (Tables)

Derivative Instruments (Tables)	6 Months Ended
	Jun. 30, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Notional Amounts of Outstanding Derivative Positions	The following table presents the absolute notional amounts related to open positions on NW Natural derivative instruments: June 30, December 31, In thousands 2019 2018 2018 Natural gas (in therms): Financial 466,280 473,900 408,850 Physical 564,500 724,450 472,275 Foreign exchange $ 7,552 $ 7,804 $ 6,936
Income Statement Presentation of Derivative Instruments	The following table reflects the income statement presentation for the unrealized gains and losses from NW Natural's derivative instruments, which also represents all derivative instruments at NW Holdings: Three Months Ended June 30, 2019 2018 In thousands Natural gas commodity Foreign exchange Natural gas commodity Foreign exchange Benefit (expense) to cost of gas $ (5,143 ) $ 246 $ 2,658 $ (56 ) Operating revenues (expense) (4,333 ) — 391 — Amounts deferred to regulatory accounts on balance sheet 8,847 (246 ) (2,915 ) 56 Total gain (loss) in pre-tax earnings $ (629 ) $ — $ 134 $ — Six Months Ended June 30, 2019 2018 In thousands Natural gas commodity Foreign exchange Natural gas commodity Foreign exchange Benefit (expense) to cost of gas $ 1,864 $ 157 $ (3,089 ) $ (210 ) Operating revenues (expense) (1,966 ) — 164 — Amounts deferred to regulatory accounts on balance sheet (182 ) (157 ) 2,980 210 Total gain (loss) in pre-tax earnings $ (284 ) $ — $ 55 $ —
Table of Estimated Collateral Calls Table	Based upon current commodity financial swap and option contracts outstanding, which reflect unrealized losses of $4.6 million at June 30, 2019 , we have estimated the level of collateral demands, with and without potential adequate assurance calls, using current gas prices and various credit downgrade rating scenarios for NW Natural as follows: Credit Rating Downgrade Scenarios In thousands (Current Ratings) A+/A3 BBB+/Baa1 BBB/Baa2 BBB-/Baa3 Speculative With Adequate Assurance Calls $ — $ — $ — $ (840 ) $ (2,179 ) Without Adequate Assurance Calls — — — (840 ) (1,910 )

Environmental Matters (Tables)

Environmental Matters (Tables)	6 Months Ended
	Jun. 30, 2019
Environmental Remediation Obligations [Abstract]
Schedule of Environmental Loss Contingencies by Site	The following table summarizes information regarding liabilities related to environmental sites, which are recorded in other current liabilities and other noncurrent liabilities in NW Natural's balance sheet: Current Liabilities Non-Current Liabilities June 30, December 31, June 30, December 31, In thousands 2019 2018 2018 2019 2018 2018 Portland Harbor site: Gasco/Siltronic Sediments $ 4,403 $ 2,174 $ 5,117 $ 44,374 $ 45,330 $ 44,351 Other Portland Harbor 2,150 1,444 2,600 5,645 3,871 6,273 Gasco/Siltronic Upland site 9,964 9,947 13,983 42,672 45,578 44,830 Central Service Center site 10 25 10 — — — Front Street site 1,051 906 11,402 10,150 10,683 3 Oregon Steel Mills — — — 179 179 179 Total $ 17,578 $ 14,496 $ 33,112 $ 103,020 $ 105,641 $ 95,636
Environmental Regulatory Table	The following table presents information regarding the total regulatory asset deferred: June 30, December 31, In thousands 2019 2018 2018 Deferred costs and interest (1) $ 43,222 $ 46,862 $ 41,883 Accrued site liabilities (2) 120,226 119,712 128,369 Insurance proceeds and interest (90,119 ) (95,824 ) (88,502 ) Total regulatory asset deferral (1) $ 73,329 $ 70,750 $ 81,750 Current regulatory assets (3) 5,089 5,594 5,601 Long-term regulatory assets (3) 68,240 65,156 76,149 (1) Includes pre-review and post-review deferred costs, amounts currently in amortization, and interest, net of amounts collected from customers. (2) Excludes 3.32% of the Front Street site liability, or $0.4 million in 2019 and $0.4 million in 2018 , as the OPUC only allows recovery of 96.68% of costs for those sites allocable to Oregon, including those that historically served only Oregon customers. (3) Environmental costs relate to specific sites approved for regulatory deferral by the OPUC and WUTC. In Oregon, NW Natural earns a carrying charge on cash amounts paid, whereas amounts accrued but not yet paid do not earn a carrying charge until expended. It also accrues a carrying charge on insurance proceeds for amounts owed to customers. In Washington, a carrying charge related to deferred amounts is expected to be determined in the current general rate case. 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)	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Discontinued Operations	DISCONTINUED OPERATIONS NW Holdings On June 20, 2018, NWN Gas Storage, then a wholly owned subsidiary of NW Natural, entered into a Purchase and Sale Agreement (the Agreement) that provides for the sale by NWN Gas Storage of all of the membership interests in Gill Ranch. Gill Ranch owns a 75% interest in the natural gas storage facility located near Fresno, California known as the Gill Ranch Gas Storage Facility. Pacific Gas and Electric Company (PG&E) owns the remaining 25% interest in the Gill Ranch Gas Storage Facility. The CPUC regulates Gill Ranch under a market-based rate model which allows for the price of storage services to be set by the marketplace. The CPUC also regulates the issuance of securities, system of accounts, and regulates intrastate storage services. The Agreement provides for an initial cash purchase price of $25.0 million (subject to a working capital adjustment), plus potential additional payments to NWN Gas Storage of up to $26.5 million in the aggregate if Gill Ranch achieves certain economic performance levels for the first three full gas storage years (April 1 of one year through March 31 of the following year) occurring after the closing and the remaining portion of the gas storage year during which the closing occurs. The closing of the transaction is subject to approval by the CPUC and other customary closing conditions. In July 2018, Gill Ranch filed an application with the CPUC for approval of this transaction. On February 14, 2019, the active parties to the CPUC proceeding filed a settlement agreement with the CPUC. On July 23, 2019, one of the parties to the settlement agreement, the CPUC’s Office of Safety Advocates (OSA), filed a motion with the CPUC to withdraw from the settlement agreement and requested a new pre-hearing conference. On July 29, 2019, Gill Ranch and the proposed purchaser filed motions with the CPUC to strike the OSA’s motion of withdrawal together with a request to supplement the evidentiary record with materials which the applicants believe demonstrate that the issues raised by the OSA are not relevant to the CPUC proceeding. We continue to strive to close this transaction by the end of 2019. As a result of the strategic shift away from the California gas storage market and the significance of Gill Ranch's financial results in 2017, we concluded that the pending sale of Gill Ranch qualified it as assets and liabilities held for sale and discontinued operations. As such, the assets and liabilities associated with Gill Ranch have been classified as discontinued operations assets and discontinued operations liabilities, respectively, and, the results of Gill Ranch are presented, net of tax, as discontinued operations separately from the results of continuing operations for all periods presented. The expenses included in the results of discontinued operations are the direct operating expenses incurred by Gill Ranch that may be reasonably segregated from the costs of NW Holdings' continuing operations. The following table presents the carrying amounts of the major components of Gill Ranch that are classified as discontinued operations assets and liabilities on the consolidated balance sheets: NW Holdings Discontinued Operations June 30, December 31, In thousands 2019 2018 2018 Assets: Accounts receivable $ 519 $ 497 $ 390 Inventories 756 646 685 Other current assets 183 413 333 Property, plant, and equipment 12,184 10,948 11,621 Less: Accumulated depreciation 6 6 7 Operating lease right of use asset 118 — — Other non-current assets 247 245 247 Total discontinued operations assets - current assets (1) $ 14,001 $ 12,743 $ 13,269 Liabilities: Accounts payable $ 1,230 $ 572 $ 873 Other current liabilities 296 436 307 Operating lease liabilities 113 — — Other non-current liabilities 11,640 11,914 11,779 Total discontinued operations liabilities - current liabilities (1) $ 13,279 $ 12,922 $ 12,959 (1) The total assets and liabilities of Gill Ranch are classified as current as of June 30, 2019 and December 31, 2018 because it is probable that the sale will be completed within one year. The following table presents the operating results of Gill Ranch, which was reported within the gas storage segment historically, and is presented net of tax on the consolidated statements of comprehensive income: NW Holdings Discontinued Operations Three Months Ended June 30, Six Months Ended June 30, In thousands, except per share data 2019 2018 2019 2018 Revenues $ 1,748 $ 1,006 $ 3,469 $ 2,083 Expenses: Operations and maintenance 2,651 1,554 4,264 2,590 General taxes 60 346 119 680 Depreciation and amortization 106 108 212 218 Other expenses and interest 229 (107 ) 466 134 Total expenses 3,046 1,901 5,061 3,622 Loss from discontinued operations before income taxes (1,298 ) (895 ) (1,592 ) (1,539 ) Income tax benefit (342 ) (236 ) (419 ) (406 ) Loss from discontinued operations, net of tax $ (956 ) $ (659 ) $ (1,173 ) $ (1,133 ) Loss from discontinued operations per share of common stock: Basic $ (0.03 ) $ (0.02 ) $ (0.04 ) $ (0.04 ) Diluted $ (0.03 ) $ (0.02 ) $ (0.04 ) $ (0.04 ) NW Natural As a result of the holding company reorganization in October 2018, NWN Energy, NWN Gas Storage, Gill Ranch, NNG Financial, NWN Water, and NW Holdings, which were direct and indirect subsidiaries of NW Natural prior to the reorganization, are no longer subsidiaries of NW Natural. As a result, NW Natural's financial statements reflect amounts related to these entities as discontinued operations for all periods presented. The expenses included in the results of discontinued operations are the direct operating expenses incurred by the entities that may be reasonably segregated from the costs of NW Natural's continuing operations. The following table presents the carrying amounts of the major components of NWN Energy, NWN Gas Storage, Gill Ranch, NNG Financial, NWN Water, and NW Holdings that are classified as discontinued operations assets and liabilities on NW Natural's consolidated balance sheets: NW Natural Discontinued Operations In thousands June 30, 2018 Assets: Cash $ 433 Accounts receivable 498 Receivables from affiliates 3,814 Inventories 646 Other current assets 482 Property, plant, and equipment 11,323 Less: Accumulated depreciation 213 Other investments 13,673 Other non-current assets 254 Discontinued operations - current assets 5,873 Discontinued operations - non-current assets 25,037 Total discontinued operations assets $ 30,910 Liabilities: Accounts payable $ 971 Taxes accrued 30 Payables to affiliates 265 Other current liabilities 1,436 Deferred tax liabilities (15,022 ) Other non-current liabilities 12,004 Discontinued operations - current liabilities 2,702 Discontinued operations - non-current liabilities (3,018 ) Total discontinued operations liabilities $ (316 ) The following table presents the operating results prior to the holding company reorganization effective October 1, 2018 of NWN Energy, NWN Gas Storage, Gill Ranch, NNG Financial, NWN Water, and NW Holdings, which were historically reported within the gas storage segment and other, and is presented net of tax on NW Natural's consolidated statements of comprehensive income: NW Natural Three Months Ended June 30, Six Months Ended June 30, In thousands, except per share data 2018 2018 Revenues $ 1,065 $ 2,198 Expenses: Operations and maintenance 1,684 2,743 General taxes 356 703 Depreciation and amortization 165 282 Other expenses and interest (150 ) 110 Total expenses 2,055 3,838 Loss from discontinued operations before income taxes (990 ) (1,640 ) Income tax benefit (263 ) (436 ) Loss from discontinued operations, net of tax $ (727 ) $ (1,204 )
Northwest Natural Gas Company [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Groups, Including Discontinued Operations		The following table presents the operating results prior to the holding company reorganization effective October 1, 2018 of NWN Energy, NWN Gas Storage, Gill Ranch, NNG Financial, NWN Water, and NW Holdings, which were historically reported within the gas storage segment and other, and is presented net of tax on NW Natural's consolidated statements of comprehensive income: NW Natural Three Months Ended June 30, Six Months Ended June 30, In thousands, except per share data 2018 2018 Revenues $ 1,065 $ 2,198 Expenses: Operations and maintenance 1,684 2,743 General taxes 356 703 Depreciation and amortization 165 282 Other expenses and interest (150 ) 110 Total expenses 2,055 3,838 Loss from discontinued operations before income taxes (990 ) (1,640 ) Income tax benefit (263 ) (436 ) Loss from discontinued operations, net of tax $ (727 ) $ (1,204 )
Northwest Holdings [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Groups, Including Discontinued Operations	The following table presents the operating results of Gill Ranch, which was reported within the gas storage segment historically, and is presented net of tax on the consolidated statements of comprehensive income: NW Holdings Discontinued Operations Three Months Ended June 30, Six Months Ended June 30, In thousands, except per share data 2019 2018 2019 2018 Revenues $ 1,748 $ 1,006 $ 3,469 $ 2,083 Expenses: Operations and maintenance 2,651 1,554 4,264 2,590 General taxes 60 346 119 680 Depreciation and amortization 106 108 212 218 Other expenses and interest 229 (107 ) 466 134 Total expenses 3,046 1,901 5,061 3,622 Loss from discontinued operations before income taxes (1,298 ) (895 ) (1,592 ) (1,539 ) Income tax benefit (342 ) (236 ) (419 ) (406 ) Loss from discontinued operations, net of tax $ (956 ) $ (659 ) $ (1,173 ) $ (1,133 ) Loss from discontinued operations per share of common stock: Basic $ (0.03 ) $ (0.02 ) $ (0.04 ) $ (0.04 ) Diluted $ (0.03 ) $ (0.02 ) $ (0.04 ) $ (0.04 )
Northwest Natural Gas Company [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Groups, Including Discontinued Operations		The following table presents the carrying amounts of the major components of NWN Energy, NWN Gas Storage, Gill Ranch, NNG Financial, NWN Water, and NW Holdings that are classified as discontinued operations assets and liabilities on NW Natural's consolidated balance sheets: NW Natural Discontinued Operations In thousands June 30, 2018 Assets: Cash $ 433 Accounts receivable 498 Receivables from affiliates 3,814 Inventories 646 Other current assets 482 Property, plant, and equipment 11,323 Less: Accumulated depreciation 213 Other investments 13,673 Other non-current assets 254 Discontinued operations - current assets 5,873 Discontinued operations - non-current assets 25,037 Total discontinued operations assets $ 30,910 Liabilities: Accounts payable $ 971 Taxes accrued 30 Payables to affiliates 265 Other current liabilities 1,436 Deferred tax liabilities (15,022 ) Other non-current liabilities 12,004 Discontinued operations - current liabilities 2,702 Discontinued operations - non-current liabilities (3,018 ) Total discontinued operations liabilities $ (316 )
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 June 30, December 31, In thousands 2019 2018 2018 Assets: Accounts receivable $ 519 $ 497 $ 390 Inventories 756 646 685 Other current assets 183 413 333 Property, plant, and equipment 12,184 10,948 11,621 Less: Accumulated depreciation 6 6 7 Operating lease right of use asset 118 — — Other non-current assets 247 245 247 Total discontinued operations assets - current assets (1) $ 14,001 $ 12,743 $ 13,269 Liabilities: Accounts payable $ 1,230 $ 572 $ 873 Other current liabilities 296 436 307 Operating lease liabilities 113 — — Other non-current liabilities 11,640 11,914 11,779 Total discontinued operations liabilities - current liabilities (1) $ 13,279 $ 12,922 $ 12,959 (1) The total assets and liabilities of Gill Ranch are classified as current as of June 30, 2019 and December 31, 2018 because it is probable that the sale will be completed within one year.

Significant Accounting Polici_4

Significant Accounting Policies - Regulatory Asset Disclosure (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Regulatory Assets [Line Items]
Regulatory Assets, Current	$ 46,688	$ 41,930	$ 41,092
Regulatory Assets, Noncurrent	318,340	371,786	339,177
Northwest Natural Gas Company [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	46,688	41,930	41,092
Regulatory Assets, Noncurrent	318,340	371,786	339,177
Northwest Natural Gas Company [Member] | Deferred Derivative Gain (Loss) [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	4,385	12,381	11,744
Regulatory Assets, Noncurrent	2,062	3,025	3,913
Northwest Natural Gas Company [Member] | Gas costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	19,195	2,873	273
Regulatory Assets, Noncurrent	2,994	9,978	28
Northwest Natural Gas Company [Member] | Environmental costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	5,089	5,601	5,594
Regulatory Assets, Noncurrent	68,240	76,149	65,156
Northwest Natural Gas Company [Member] | Decoupling [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	1,680	9,140	10,232
Regulatory Assets, Noncurrent	37	2,545	1,636
Northwest Natural Gas Company [Member] | Pension balancing [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	5,009	0	0
Regulatory Assets, Noncurrent	50,080	74,173	67,527
Northwest Natural Gas Company [Member] | Income taxes [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	2,209	2,218	2,217
Regulatory Assets, Noncurrent	17,758	19,185	19,267
Northwest Natural Gas Company [Member] | Pension and other postretirement benefit liabilities [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Noncurrent	168,137	174,993	171,186
Northwest Natural Gas Company [Member] | Other [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	9,121	9,717	11,032
Regulatory Assets, Noncurrent	$ 9,032	$ 11,738	$ 10,464

Significant Accounting Polici_5

Significant Accounting Policies - Regulatory Liability Disclosure (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	$ 32,484	$ 47,436	$ 34,275
Regulatory Liability, Noncurrent	605,036	611,560	602,294
Northwest Natural Gas Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	32,484	47,436	34,275
Regulatory Liability, Noncurrent	605,036	611,560	602,294
Northwest Natural Gas Company [Member] | Gas costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	5,630	17,182	20,906
Regulatory Liability, Noncurrent	226	552	3,460
Northwest Natural Gas Company [Member] | Deferred Derivative Gain (Loss) [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	1,944	8,740	1,938
Regulatory Liability, Noncurrent	670	725	1,077
Northwest Natural Gas Company [Member] | Decoupling [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	857	2,264	2,153
Regulatory Liability, Noncurrent	74	0	410
Northwest Natural Gas Company [Member] | Income taxes [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	7,763	0	0
Regulatory Liability, Noncurrent	202,422	225,408	222,734
Northwest Natural Gas Company [Member] | Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	16,290	19,250	9,278
Regulatory Liability, Noncurrent	11,299	4,411	4,368
Northwest Natural Gas Company [Member] | Accrued asset removal costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Noncurrent	$ 390,345	$ 380,464	$ 370,245

Significant Accounting Polici_6

Significant Accounting Policies Significant Accounting Policies - AOCI Tax Effects ASU 2018-02 (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stranded Deferred Tax Remeasurement Benefit	$ 0	$ 0	$ 1,366	$ 0
Accounting Standards Update 2018-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stranded Deferred Tax Remeasurement Benefit			$ 1,400

Significant Accounting Polici_7

Significant Accounting Policies - Leases ASU 2016-02 (Details) - USD ($)	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right of use asset	$ 5,013,000	$ 0	$ 0
Operating Lease, Liability	4,992,000
Property, plant, and equipment	3,355,811,000	3,414,490,000	3,298,856,000
Other Liabilities, Noncurrent	129,835,000	147,763,000	140,163,000
Northwest Natural Gas Company [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right of use asset	4,797,000	0	0
Operating Lease, Liability	4,775,000
Property, plant, and equipment	3,337,005,000	3,410,439,000	3,298,481,000
Other Liabilities, Noncurrent	129,736,000	147,668,000	$ 140,073,000
Accounting Standards Update 2016-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	0
Initial Direct or Capitalized Lease Cost to be De-recognized, Legacy Leases	0
Operating lease right of use asset	7,300,000
Operating Lease, Liability	7,300,000
Accounting Standards Update 2016-02 [Member] | Northwest Natural Gas Company [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right of use asset	7,000,000
Operating Lease, Liability	$ 7,000,000
Accounting Standards Update 2016-02 [Member] | New Headquarters Lease [Member] | Build to Suit Lease [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Property, plant, and equipment		26,000,000
Other Liabilities, Noncurrent		$ 26,000,000

Earnings Per Share (Details)

Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Statement [Line Items]
Net income from continuing operations	$ 2,051	$ (339)	$ 45,469	$ 41,672
Loss from discontinued operations, net of tax	(956)	(659)	(1,173)	(1,133)
Net income	$ 1,095	$ (998)	$ 44,296	$ 40,539
Average common shares outstanding:
Average common shares outstanding - basic (in shares)	29,337	28,791	29,123	28,772
Additional shares for stock-based compensation plans	57	0	63	53
Average common shares outstanding - diluted (in shares)	29,394	28,791	29,186	28,825
Earnings from continuing operations per share of common stock:
Basic (in dollars per share)	$ 0.07	$ (0.01)	$ 1.56	$ 1.45
Diluted (in dollars per share)	0.07	(0.01)	1.56	1.45
Earnings (loss) per share of common stock
Basic (in dollars per share)	0.04	(0.03)	1.52	1.41
Diluted (in dollars per share)	$ 0.04	$ (0.03)	$ 1.52	$ 1.41
Antidilutive shares	1	53	2	10
Discontinued Operations, Held-for-sale [Member] | Gill Ranch [Member]
Income Statement [Line Items]
Loss from discontinued operations, net of tax	$ (956)	$ (659)	$ (1,173)	$ (1,133)
Loss from discontinued operations per share of common stock:
Basic (in dollars per share)	$ (0.03)	$ (0.02)	$ (0.04)	$ (0.04)
Diluted (in dollars per share)	$ (0.03)	$ (0.02)	$ (0.04)	$ (0.04)

Segment Information - Narrative

Segment Information - Narrative (Details)	6 Months Ended
	Jun. 30, 2019
Operating Segments [Member]
Segment Reporting Information [Line Items]
Number of Reportable Segments	1
Oregon [Member] | Northwest Holdings and Northwest Natural [Member] | Natural Gas Distribution [Member]
Segment Reporting Information [Line Items]
Percent Of Pre Tax Income From Gas Storage Retained When The Costs Of The Capacity Are Not In Utility Rates	80.00%
Percent Of Pre Tax Income From Gas Storage Retained When The Costs Of The Capacity Are In Utility Rates	10.00%
Percent Of Pre Tax Income From Gas Storage Credited To Deferred Regulatory Account	20.00%
Percent Of Pre Tax Income From Gas Storage Credited To Deferred Regulatory Account When In Rates	90.00%

Segment Information - Schedule

Segment Information - Schedule of Summarized Financial Information by Segment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Segment Reporting Information [Line Items]
Operating revenues	$ 123,443	$ 124,567	$ 408,791	$ 388,202
Depreciation and amortization	22,387	21,147	43,959	42,022
Income from operations	16,098	8,269	92,143	76,020
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	2,051	(339)	45,469	41,672
Capital expenditures			91,147	102,370
Total assets	3,238,131	2,986,760	3,238,131	2,986,760	$ 3,242,662
Discontinued operations - current assets	14,001	12,743	14,001	12,743	13,269
Discontinued operations - total assets		12,700		12,700
Natural Gas Distribution [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	117,984	118,515	397,025	376,448
Depreciation and amortization	21,992	20,766	43,241	41,309
Income from operations	14,657	4,545	87,555	69,301
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	1,212	(2,970)	42,418	36,913
Capital expenditures	41,912	43,801	90,518	100,695
Total assets	3,089,944	2,907,936	3,089,944	2,907,936	3,141,969
Other Northwest Natural [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating revenues	4,258	6,048	10,063	11,750
Depreciation and amortization	251	324	506	649
Income from operations	2,583	3,860	6,329	6,842
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	1,842	2,699	4,531	4,830
Capital expenditures	105	1,240	157	1,675
Total assets	48,749	51,993	48,749	51,993	50,767
Northwest Natural Gas Company [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	122,242	124,563	407,088	388,198
Depreciation and amortization	22,243	21,090	43,747	41,958
Income from operations	17,240	8,405	93,884	76,143
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	3,054	(271)	46,949	41,743
Capital expenditures	42,017	45,041	90,675	102,370
Total assets	3,138,693	2,959,929	3,138,693	2,959,929	3,192,736
Other Northwest Holdings [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating revenues	1,201	4	1,703	4
Depreciation and amortization	144	57	212	64
Income from operations	(1,142)	(136)	(1,741)	(123)
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	(1,003)	(68)	(1,480)	(71)
Capital expenditures	366	0	472	0
Total assets	85,437	14,088	85,437	14,088	36,657
Northwest Natural Gas Company [Member]
Segment Reporting Information [Line Items]
Operating revenues	122,242	124,563	407,088	388,198
Depreciation and amortization	22,243	21,090	43,747	41,958
Income from operations	17,240	8,405	93,884	76,143
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	3,054	(271)	46,949	41,743
Capital expenditures			90,675	102,370
Total assets	3,138,693	2,990,839	3,138,693	2,990,839	3,192,736
Discontinued operations - current assets	0	5,873	0	5,873	0
Discontinued operations - total assets	0	3,018	0	3,018	0
Northwest Natural Gas Company [Member] | Natural Gas Distribution [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	117,984	118,515	397,025	376,448
Northwest Natural Gas Company [Member] | Other Northwest Natural [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating revenues	4,258	6,048	10,063	11,750
Northwest Natural Gas Company [Member] | Northwest Natural Gas Company [Member]
Segment Reporting Information [Line Items]
Operating revenues	122,242	124,563	407,088	388,198
Northwest Natural Gas Company [Member]
Segment Reporting Information [Line Items]
Discontinued operations - total assets		30,900		30,900
Parent Company [Member]
Segment Reporting Information [Line Items]
Operating revenues	123,443	124,567	408,791	388,202
Depreciation and amortization	22,387	21,147	43,959	42,022
Income from operations	16,098	8,269	92,143	76,020
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	2,051	(339)	45,469	41,672
Capital expenditures	42,383	45,041	91,147	102,370
Total assets	$ 3,224,130	$ 2,974,017	$ 3,224,130	$ 2,974,017	$ 3,229,393

Segment Information - Additiona

Segment Information - Additional Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment Reporting Information [Line Items]
Operating revenues	$ 123,443	$ 124,567	$ 408,791	$ 388,202
Cost of gas	35,107	42,053	140,564	150,159
Environmental remediation	(2,656)	1,882	6,291	6,506
Operating Segments [Member] | Natural Gas Distribution [Member]
Segment Reporting Information [Line Items]
Natural Gas Distribution revenues	115,792	118,435	394,775	376,341
Other regulated services	2,192	80	2,250	107
Operating revenues	117,984	118,515	397,025	376,448
Cost of gas	35,163	42,107	140,676	150,271
Environmental remediation	(2,656)	1,882	6,291	6,506
Revenue taxes	4,496	4,780	16,422	17,209
NGD margin	$ 80,981	$ 69,746	$ 233,636	$ 202,462

Common Stock (Details)

Common Stock (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	6 Months Ended
	Jun. 07, 2019	Jun. 30, 2019
Class of Stock [Line Items]
Shares Issued, Price Per Share	$ 67
Stock Issued During Period, Value, New Issues		$ 92.8
Base shares offered [Member]
Class of Stock [Line Items]
Stock Issued During Period, Shares, New Issues		1,250,000
Over-Allotment Option [Member]
Class of Stock [Line Items]
Stock Issued During Period, Shares, New Issues		187,500
Sale of stock, offering period	30 days
Total shares issued [Member]
Class of Stock [Line Items]
Stock Issued During Period, Shares, New Issues		1,437,500
Maximum [Member]
Class of Stock [Line Items]
Payments of Stock Issuance Costs		$ 0.4

Leases - Lease Revenue (Details

Leases - Lease Revenue (Details)	3 Months Ended	6 Months Ended
	Jun. 30, 2019USD ($)	Jun. 30, 2019USD ($)
Lessor, Lease, Description [Line Items]
Lessor, Sales-type Lease, Renewal Term	50 years	50 years
Lessor, Sales-type Lease, Term of Contract	30 years	30 years
Residual Value of Leased Asset	$ 3,800,000	$ 3,800,000
Lease Revenue [Abstract]
Operating leases	47,000	95,000
Sales-type leases	2,085,000	2,145,000
Total lease revenue	2,132,000	2,240,000
Operating Leases Payment to be Received [Abstract]
Operating Lease, Payments to be Received, Remainder of Fiscal Year	58,000	58,000
Operating Lease, Payments to be Received, Two Years	61,000	61,000
Operating Lease, Payments to be Received, Three Years	49,000	49,000
Operating Lease, Payments to be Received, Four Years	45,000	45,000
Operating Lease, Payments to be Received, Five Years	45,000	45,000
Operating Lease, Payments to be Received, Thereafter	138,000	138,000
Total lease revenue	396,000	396,000
Total Lease Payments to be Received [Abstract]
Lease Payments to be Received, Remainder of Fiscal Year	9,766,000	9,766,000
Lease Payments to be Received, Two Years	18,289,000	18,289,000
Lease Payments to be Received, Three Years	17,567,000	17,567,000
Lease Payments to be Received, Four Years	17,071,000	17,071,000
Lease Payments to be Received, Five Years	16,602,000	16,602,000
Lease Payments to be Received, Thereafter	280,745,000	280,745,000
Total lease revenue	$ 360,040,000	$ 360,040,000
Compressed Natural Gas Lease [Member]
Lessor, Lease, Description [Line Items]
Lessor, Sales-type Lease, Term of Contract	10 years	10 years
Residual Value of Leased Asset	$ 0	$ 0
Variable Lease, Payment		0
North Mist Lease [Member]
Lessor, Lease, Description [Line Items]
Residual Value of Leased Asset	0	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	9,708,000	9,708,000
Sales-type Lease, Payments to be Received, Two Years	18,228,000	18,228,000
Sales-type Lease, Payments to be Received, Three Years	17,518,000	17,518,000
Sales-type Lease, Payments to be Received, Four Years	17,026,000	17,026,000
Sales-type Lease, Payments to be Received, Five Years	16,557,000	16,557,000
Sales-type Lease, Payments to be Received, Thereafter	280,607,000	280,607,000
Total lease revenue	359,644,000	359,644,000
Less: imputed interest	208,877,000	208,877,000
Total leases receivable	$ 150,767,000	$ 150,767,000

Revenue - Disaggregation of Rev

Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	$ 117,578	$ 120,778	$ 420,071	$ 384,708
Revenues	123,443	124,567	408,791	388,202
Operating leases	47		95
Natural Gas Sales [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	112,015	114,726	408,201	372,954
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	2,740	2,737	5,523	5,314
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	460	2,140	1,966	3,719
Appliance Center Revenue [Member] | Transferred at Point in Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,058	1,171	2,574	2,717
Other revenue [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,305	4	1,807	4
Alternative revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	3,733	3,663	(13,520)	3,291
Leasing revenue [Member]
Disaggregation of Revenue [Line Items]
Operating leases	2,132	126	2,240	203
Northwest Natural Gas Company [Member]
Disaggregation of Revenue [Line Items]
Revenues	122,242	124,563	407,088	388,198
Northwest Natural Gas Company [Member] | Northwest Natural Gas Company [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	116,377	120,774	418,368	384,704
Revenues	122,242	124,563	407,088	388,198
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	112,015	114,726	408,201	372,954
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	2,740	2,737	5,523	5,314
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	460	2,140	1,966	3,719
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	1,058	1,171	2,574	2,717
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	104	0	104	0
Northwest Natural Gas Company [Member] | Northwest Natural Gas Company [Member] | Alternative revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	3,733	3,663	(13,520)	3,291
Northwest Natural Gas Company [Member] | Northwest Natural Gas Company [Member] | Leasing revenue [Member]
Disaggregation of Revenue [Line Items]
Operating leases	2,132	126	2,240	203
Operating Segments [Member] | Natural Gas Distribution [Member]
Disaggregation of Revenue [Line Items]
Revenues	117,984	118,515	397,025	376,448
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	112,119	114,726	408,305	372,954
Revenues	117,984	118,515	397,025	376,448
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	112,015	114,726	408,201	372,954
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	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	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	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	104	0	104	0
Operating Segments [Member] | Natural Gas Distribution [Member] | Northwest Natural Gas Company [Member] | Alternative revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	3,733	3,663	(13,520)	3,291
Operating Segments [Member] | Natural Gas Distribution [Member] | Northwest Natural Gas Company [Member] | Leasing revenue [Member]
Disaggregation of Revenue [Line Items]
Operating leases	2,132	126	2,240	203
Operating Segments [Member] | Northwest Natural Gas Company [Member]
Disaggregation of Revenue [Line Items]
Revenues	122,242	124,563	407,088	388,198
Corporate, Non-Segment [Member] | Other Northwest Natural [Member]
Disaggregation of Revenue [Line Items]
Revenues	4,258	6,048	10,063	11,750
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	4,258	6,048	10,063	11,750
Revenues	4,258	6,048	10,063	11,750
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	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	2,740	2,737	5,523	5,314
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	460	2,140	1,966	3,719
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	1,058	1,171	2,574	2,717
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	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	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	0	0
Corporate, Non-Segment [Member] | Other Northwest Holdings [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,201	4	1,703	4
Revenues	1,201	4	1,703	4
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	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	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	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	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	1,201	4	1,703	4
Corporate, Non-Segment [Member] | Other Northwest Holdings [Member] | Alternative revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Corporate, Non-Segment [Member] | Other Northwest Holdings [Member] | Leasing revenue [Member]
Disaggregation of Revenue [Line Items]
Operating leases	$ 0	$ 0	$ 0	$ 0

Leases - Lease Expense (Details

Leases - Lease Expense (Details) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019USD ($)	Jun. 30, 2019USD ($)
Lessee, Lease, Description [Line Items]
Residual Value of Leased Asset	$ 3,800	$ 3,800
Lease Expense [Abstract]
Operating Lease, Expense	1,201	2,389
Short-term Lease, Cost	$ 331	$ 491
Minimum [Member]
Operating Lease Terms [Abstract]
Lessee, Operating Lease, Term of Contract	1 year	1 year
Maximum [Member]
Operating Lease Terms [Abstract]
Lessee, Operating Lease, Term of Contract	11 years	11 years
Northwest Natural Gas Company [Member]
Lease Expense [Abstract]
Operating Lease, Expense	$ 1,155	$ 2,297
Short-term Lease, Cost	331	491
Other Northwest Holdings [Member] | Corporate, Non-Segment [Member]
Lease Expense [Abstract]
Operating Lease, Expense	46	92
Short-term Lease, Cost	$ 0	$ 0

Revenue - Revenue, Remaining Pe

Revenue - Revenue, Remaining Performance Obligation (Details) $ in Millions	Jun. 30, 2019USD ($)
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]: 2019-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Year	2019
Revenue, Remaining Performance Obligation, Amount	$ 7.4
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Year	2020
Revenue, Remaining Performance Obligation, Amount	$ 13.7
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Year	2021
Revenue, Remaining Performance Obligation, Amount	$ 12.8
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Year	2022
Revenue, Remaining Performance Obligation, Amount	$ 9.1
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Year	2023
Revenue, Remaining Performance Obligation, Amount	$ 7.5
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 58.4

Leases - Lease Asset and Liabil

Leases - Lease Asset and Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Jun. 30, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jun. 30, 2018
Operating Lease Asset and Liabilities [Abstract]
Operating lease right of use asset	$ 5,013	$ 5,013	$ 0			$ 0
Operating lease liabilities current liabilities	4,271	4,271	0			0
Operating lease liabilities noncurrent liabilities	721	721	0			0
Total operating lease liabilities	4,992	4,992
Maturity of Operating Lease Liabilities [Abstract]
Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year	2,391	2,391
Lessee, Operating Lease, Liability, Payments, Due Year Two	2,082	2,082
Lessee, Operating Lease, Liability, Payments, Due Year Three	129	129
Lessee, Operating Lease, Liability, Payments, Due Year Four	93	93
Lessee, Operating Lease, Liability, Payments, Due Year Five	71	71
Lessee, Operating Lease, Liability, Payments, Due after Year Five	497	497
Lessee, Operating Lease, Liability, Payments, Due	5,263	5,263
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	271	271
Total operating lease liabilities	4,992	4,992
Operating lease liabilities current liabilities	4,271	4,271	0			0
Operating lease liabilities noncurrent liabilities	721	721	0			0
Lease Not Yet Commenced [Abstract]
Lessee, Operating Lease, Liability, Payments, Due	5,263	5,263
Leases Cash Flow [Abstract]
Operating cash flows from operating leases	1,159	2,293
Operating leases		7,291
Finance Leases [Abstract]
Finance Lease, Right-of-Use Asset	300	300
Prior Period Disclosures [Abstract]
Operating Leases, Rent Expense			5,900	$ 7,300	$ 5,900
Other Northwest Holdings [Member] | Corporate, Non-Segment [Member]
Operating Lease Asset and Liabilities [Abstract]
Operating lease right of use asset	216	216
Operating lease liabilities current liabilities	130	130
Operating lease liabilities noncurrent liabilities	87	87
Total operating lease liabilities	217	217
Maturity of Operating Lease Liabilities [Abstract]
Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year	93	93
Lessee, Operating Lease, Liability, Payments, Due Year Two	102	102
Lessee, Operating Lease, Liability, Payments, Due Year Three	28	28
Lessee, Operating Lease, Liability, Payments, Due Year Four	0	0
Lessee, Operating Lease, Liability, Payments, Due Year Five	0	0
Lessee, Operating Lease, Liability, Payments, Due after Year Five	0	0
Lessee, Operating Lease, Liability, Payments, Due	223	223
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	6	6
Total operating lease liabilities	217	217
Operating lease liabilities current liabilities	130	130
Operating lease liabilities noncurrent liabilities	87	87
Lease Not Yet Commenced [Abstract]
Lessee, Operating Lease, Liability, Payments, Due	223	223
Leases Cash Flow [Abstract]
Operating cash flows from operating leases	44	87
Operating leases		304
Northwest Natural Gas Company [Member]
Operating Lease Asset and Liabilities [Abstract]
Operating lease right of use asset	4,797	4,797	0			0
Operating lease liabilities current liabilities	4,141	4,141	0			0
Operating lease liabilities noncurrent liabilities	634	634	0			0
Total operating lease liabilities	$ 4,775	$ 4,775
Operating Lease, Weighted Average Remaining Lease Term	1 year 21 days	1 year 21 days
Operating Lease, Weighted Average Discount Rate, Percent	3.82%	3.82%
Maturity of Operating Lease Liabilities [Abstract]
Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year	$ 2,298	$ 2,298
Lessee, Operating Lease, Liability, Payments, Due Next Twelve Months			5,368
Lessee, Operating Lease, Liability, Payments, Due Year Two	1,980	1,980	4,812
Lessee, Operating Lease, Liability, Payments, Due Year Three	101	101	7,077
Lessee, Operating Lease, Liability, Payments, Due Year Four	93	93	7,223
Lessee, Operating Lease, Liability, Payments, Due Year Five	71	71	7,304
Lessee, Operating Lease, Liability, Payments, Due after Year Five	497	497	149,881
Lessee, Operating Lease, Liability, Payments, Due	5,040	5,040	181,665
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	265	265
Total operating lease liabilities	4,775	4,775
Operating lease liabilities current liabilities	4,141	4,141	0			0
Operating lease liabilities noncurrent liabilities	634	634	0			$ 0
Lease Not Yet Commenced [Abstract]
Lessee, Operating Lease, Liability, Payments, Due	5,040	5,040	$ 181,665
Leases Cash Flow [Abstract]
Operating cash flows from operating leases	1,115	2,206
Operating leases		6,987
New Headquarters Lease [Member]
Maturity of Operating Lease Liabilities [Abstract]
Lessee, Operating Lease, Liability, Payments, Due	$ 160,000	$ 160,000
Lease Not Yet Commenced [Abstract]
Lessee, Operating Lease, Lease Not yet Commenced, Term of Contract	20 years	20 years
Lessee, Operating Lease, Liability, Payments, Due	$ 160,000	$ 160,000
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	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	7 years

Stock-Based Compensation (Detai

Stock-Based Compensation (Details) - Long Term Incentive Plan $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 2019USD ($)$ / sharesshares
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares granted (in shares)	0
Award vesting period	3 years
Unrecognized compensation costs | $	$ 600
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)	33,804
Weighted-average grant date fair value (in dollars per share) | $ / shares	$ 64.93
Unrecognized compensation costs | $	$ 4,000
Unrecognized Compensation Cost, Period for Recognition	through 2023
A 2018 Award and 2019 Award [Member] | Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense | $	$ 0
Target Achieved [Member] | A 2018 Award [Member] | Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share Based Compensation Award Target Share	32,497
Target Achieved [Member] | A 2019 Award [Member] | Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share Based Compensation Award Target Share	36,250

Debt Short-term Debt (Details)

Debt Short-term Debt (Details) - USD ($)	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Short-term Debt [Line Items]
Short-term debt	$ 20,080,000	$ 217,620,000	$ 47,100,000
Northwest Natural Gas Company [Member]
Short-term Debt [Line Items]
Short-term debt	0	$ 217,500,000	$ 47,100,000
Commercial Paper	$ 0

Long-Term Debt (Details)

Long-Term Debt (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Debt Instrument [Line Items]
Long-term Debt	$ 910,397	$ 736,236	$ 758,680
Unamortized debt issuance costs	$ 6,435	5,577	6,020
Ratio of Indebtedness to Net Capital	0.515
Northwest Natural Gas Company [Member]
Debt Instrument [Line Items]
Long-term Debt	$ 873,306	734,123	758,680
Unamortized debt issuance costs	$ 6,394	$ 5,577	$ 6,020
Northwest Natural Gas Company [Member] | Minimum [Member]
Debt Instrument [Line Items]
Stated interest rate	2.822%
Weighted average interest rate	4.786%
Northwest Natural Gas Company [Member] | Maximum [Member]
Debt Instrument [Line Items]
Stated interest rate	9.05%
Note 3869 Series Due 2049 [Member] | Northwest Natural Gas Company [Member]
Debt Instrument [Line Items]
Stated interest rate	3.869%
Proceeds from Issuance of Debt	$ 90,000
Note 3141 Series Due 2029 [Member] | Northwest Natural Gas Company [Member]
Debt Instrument [Line Items]
Stated interest rate	3.141%
Proceeds from Issuance of Debt	$ 50,000
Two-year Term Loan Due 2021 [Member]
Debt Instrument [Line Items]
Stated interest rate	2.86%
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	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Debt Instrument [Line Items]
Gross long-term debt	$ 916,832	$ 741,813	$ 764,700
Unamortized debt issuance costs	(6,435)	(5,577)	(6,020)
Carrying amount	910,397	736,236	758,680
Estimated fair value	970,205	762,335	792,623
Northwest Natural Gas Company [Member]
Debt Instrument [Line Items]
Gross long-term debt	879,700	739,700	764,700
Unamortized debt issuance costs	(6,394)	(5,577)	(6,020)
Carrying amount	873,306	734,123	758,680
Estimated fair value	$ 933,167	$ 760,222	$ 792,623

Pension and Other Postretirem_3

Pension and Other Postretirement Benefit Costs - Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 1,516		$ 1,807	$ 3,033	$ 3,614
Interest cost	4,661		4,183	9,323	8,366
Expected return on plan assets	(5,207)		(5,150)	(10,414)	(10,301)
Amortization of net actuarial loss	2		10	4	21
Defined Benefit Plan, Amortization of Gain (Loss)	3,603		4,524	7,206	9,047
Net periodic benefit cost	4,575		5,374	9,152	10,747
Amount allocated to construction	(596)		(685)	(1,182)	(1,367)
Amount deferred to regulatory balancing account(1)	0		(2,747)	0	(5,503)
Defined Benefit Plan Net Periodic Benefit Cost Charged To Expense	3,979		1,942	7,970	3,877
Regulatory Pension Disallowance	0		0	10,500	0
Amortization of Regulatory Balancing Account	1,281	$ 12,500	0	13,792	0
Net amount charged to expense	5,260		1,942	32,262	3,877
Other Postretirement Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	67		79	135	159
Interest cost	283		241	564	482
Expected return on plan assets	0		0	0	0
Amortization of net actuarial loss	(117)		(117)	(234)	(234)
Defined Benefit Plan, Amortization of Gain (Loss)	96		112	193	222
Net periodic benefit cost	329		315	658	629
Amount allocated to construction	(23)		(28)	(47)	(55)
Amount deferred to regulatory balancing account(1)	0		0	0	0
Defined Benefit Plan Net Periodic Benefit Cost Charged To Expense	306		287	611	574
Regulatory Pension Disallowance	0		0	0	0
Amortization of Regulatory Balancing Account	0		0	0	0
Net amount charged to expense	$ 306		$ 287	$ 611	$ 574
Minimum [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan Net Periodic Benefit Costs Overhead Charge Percentage				25.00%
Maximum [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan Net Periodic Benefit Costs Overhead Charge Percentage				35.00%

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		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss) [Abstract]
Beginning balance	$ (8,439)	$ (8,284)	$ (7,188)	$ (8,438)
Amortization of actuarial losses	156	209	312	418
Stranded Deferred Tax Remeasurement Benefit	0	0	(1,366)	0
Total reclassifications before tax	156	209	(1,054)	418
Tax (benefit) expense	(41)	(56)	(82)	(111)
Total reclassifications for the period	115	153	(1,136)	307
Ending balance	$ (8,324)	$ (8,131)	$ (8,324)	$ (8,131)

Pension and Other Postretirem_5

Pension and Other Postretirement Benefit Costs - Narrative (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Pension and Other Postretirement Benefits Cost (Reversal of Cost) [Abstract]
Defined benefit pension plan cash contributions	$ 4.7
Estimated future employer contributions in next fiscal year	6.3
Employer contributions	$ 3.8	$ 3.5

Income Tax (Details)

Income Tax (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Income taxes at statutory rates (federal and state)	$ 694	$ (135)	$ 15,007	$ 15,233
Differences required to be flowed-through by regulatory commissions	(37)	(14)	(5,297)	835
Other, net	(32)	(7)	(410)	(592)
Total provision for income taxes on continuing operations	$ 625	$ (156)	$ 9,300	$ 15,476
Effective tax rate for continuing operations	23.40%	31.50%	17.00%	27.10%
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent			21.00%		35.00%
Northwest Natural Gas Company [Member]
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Income taxes at statutory rates (federal and state)	$ 1,055	$ (107)	$ 15,540	$ 15,264
Differences required to be flowed-through by regulatory commissions	(37)	(14)	(5,297)	835
Other, net	(33)	(7)	(410)	(592)
Total provision for income taxes on continuing operations	$ 985	$ (128)	$ 9,833	$ 15,507
Effective tax rate for continuing operations	24.40%	32.10%	17.30%	27.10%

Property, Plant and Equipment_3

Property, Plant and Equipment (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Property, Plant and Equipment [Line Items]
Property, plant, and equipment	$ 3,355,811	$ 3,414,490	$ 3,298,856
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	1,016,185	993,118	984,998
Property, Plant and Equipment, Net	2,339,626	2,421,372	2,313,858
Other Liabilities, Noncurrent	129,835	147,763	140,163
Natural Gas Distribution [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment	3,193,121	3,134,122	3,035,089
Public Utilities, Property, Plant and Equipment, Construction Work in Progress	75,045	204,978	192,496
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	997,111	974,252	966,766
Property, Plant and Equipment, Net	2,271,055	2,364,848	2,260,819
Other Northwest Natural [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment	63,385	66,009	65,548
Public Utilities, Property, Plant and Equipment, Construction Work in Progress	5,454	5,330	5,347
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	18,650	18,603	18,024
Property, Plant and Equipment, Net	50,189	52,736	52,871
Northwest Natural Gas Company [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Net	2,321,244	2,417,584	2,313,690
Other Northwest Holdings [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment	18,806	4,051	376
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	424	263	208
Property, Plant and Equipment, Net	18,382	3,788	168
Northwest Holdings and Northwest Natural [Member]
Property, Plant and Equipment [Line Items]
Property, Plant, Equipment non-cash	$ 32,923	23,676	22,112
New Headquarters Lease [Member]
Property, Plant and Equipment [Line Items]
Lessee, Operating Lease, Lease Not yet Commenced, Term of Contract	20 years
New Headquarters Lease [Member] | Accounting Standards Update 2016-02 [Member] | Build to Suit Lease [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment		26,000
Other Liabilities, Noncurrent		26,000
Northwest Natural Gas Company [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment	$ 3,337,005	3,410,439	3,298,481
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	1,015,761	992,855	984,791
Property, Plant and Equipment, Net	2,321,244	2,417,584	2,313,690
Other Liabilities, Noncurrent	129,736	$ 147,668	$ 140,073
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)	6 Months Ended
	Jun. 30, 2019USD ($)
Reserve Quantities [Line Items]
Total cumulative gas reserves investment	$ 188,000,000
Term of hedge rate	10 years
Encana Oil & Gas (USA) Inc.
Reserve Quantities [Line Items]
Gas reserves investment	$ 178,000,000
Jonah Energy LLC
Reserve Quantities [Line Items]
Gas reserves investment	10,000,000
Additional rate per therm	$ 0.4725

Gas Reserves - Investment (Deta

Gas Reserves - Investment (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Reserve Quantities [Line Items]
Gas reserves	$ 17,206	$ 16,647	$ 16,579
Gas reserves, non-current	170,101	170,660	170,958
Less: Accumulated amortization	113,930	104,463	95,596
Total gas reserves	73,377	82,844	91,941
Less: Deferred taxes on gas reserves	26,995	20,071	20,381
Net investment in gas reserves	46,382	62,773	71,560
Jonah Energy LLC
Reserve Quantities [Line Items]
Total Gas Reserves Investment	$ 4,300	$ 4,800	$ 5,500

Investments (Details)

Investments (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Schedule of Equity Method Investments [Line Items]
Investment balance in TWH	$ 13.4	$ 13.4	$ 13.4
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	$ 13.4	$ 13.4	$ 13.4
Northwest Holdings [Member]
Schedule of Equity Method Investments [Line Items]
Ownership percentage of TWH	50.00%
TransCanada American Investments Ltd. [Member]
Schedule of Equity Method Investments [Line Items]
Ownership percentage of TWH	50.00%

Business Combinations Busines_3

Business Combinations Business Combinations (Details)	6 Months Ended		12 Months Ended
	Jun. 30, 2019USD ($)	Jun. 30, 2018USD ($)shares	Dec. 31, 2018USD ($)
Business Acquisition [Line Items]
Business Combination, Control Obtained Description			Through the purchase of all of the outstanding shares of Falls Water, NWN Water acquired the net assets and 100% control of Falls Water.
Goodwill	$ 49,393,000	$ 0	$ 8,954,000
Goodwill, Impairment Loss	0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets [Abstract]
Goodwill	49,393,000	0	$ 8,954,000
Sunriver [Member]
Business Acquisition [Line Items]
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual	600,000
Business Combination, Consideration Transferred	$ 55,200,000
Business Acquisition, Connections of Acquired Business	9,400
Goodwill	$ 40,153,000
Business Acquisition, Goodwill, Expected Tax Deductible Amount	50,700,000
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	211,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment	14,009,000
Goodwill	40,153,000
Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Assets	828,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets	55,201,000
Falls Water Co [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred		$ 8,500,000
Business Combination, Consideration Transferred, Shares | shares		125,000
Business Acquisition, Connections of Acquired Business			5,300
Goodwill			$ 6,400,000
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]
Goodwill			6,400,000
Other insignificant acquisitions [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred	$ 700,000		$ 2,800,000
Number of Businesses Acquired	1		3

Derivative Instruments Notional

Derivative Instruments Notional Amounts (Details) - Northwest Natural Gas Company [Member] therm in Thousands, $ in Thousands	Jun. 30, 2019USD ($)therm	Dec. 31, 2018USD ($)therm	Jun. 30, 2018USD ($)therm
Financial [Member] | Gas Year 2018 - 2019 [Member]
Derivative [Line Items]
TargetHedgeAchieved	48.00%
Financial [Member] | Gas Year 2017 - 2018 [Member]
Derivative [Line Items]
TargetHedgeAchieved	49.00%
Physical [Member] | Gas Year 2018 - 2019 [Member]
Derivative [Line Items]
TargetHedgeAchieved	24.00%
Physical [Member] | Gas Year 2017 - 2018 [Member]
Derivative [Line Items]
TargetHedgeAchieved	26.00%
Natural Gas Therms [Member] | Financial [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	466,280	408,850	473,900
Natural Gas Therms [Member] | Physical [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	564,500	472,275	724,450
Foreign Exchange Contract [Member]
Derivative [Line Items]
Foreign exchange | $	$ 7,552	$ 6,936	$ 7,804

Derivative Instruments Fair Val

Derivative Instruments Fair Value (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Derivative [Line Items]
Derivative, Fair Value, Net	$ (3.9)	$ (5.7)	$ (12.5)

Unrealized and Realized Gain_Lo

Unrealized and Realized Gain/Loss (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Financial [Member]
Derivative [Line Items]
Derivative, Gain on Derivative			$ 10,400
Derivative, Loss on Derivative	$ (900)	$ (4,700)	(13,700)
Northwest Holdings and Northwest Natural [Member] | Natural gas commodity
Derivative [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	629	(134)	284	$ (55)
Northwest Holdings and Northwest Natural [Member] | Foreign exchange
Derivative [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	0	0	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	5,143	2,658	(1,864)	(3,089)
Northwest Holdings and Northwest Natural [Member] | Benefit (expense) to cost of gas | Foreign exchange
Derivative [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	(246)	56	(157)	210
Northwest Holdings and Northwest Natural [Member] | Sales [Member] | Natural gas commodity
Derivative [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	4,333	(391)	1,966	(164)
Northwest Holdings and Northwest Natural [Member] | Sales [Member] | Foreign exchange
Derivative [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	0	0	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	(8,847)	2,915	182	(2,980)
Deferred Derivative Gain (Loss) [Member] | Northwest Holdings and Northwest Natural [Member] | Foreign exchange
Derivative [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	$ 246	$ (56)	$ 157	$ (210)

Derivative Instruments Credit R

Derivative Instruments Credit Rating (Details) - USD ($)	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Derivative [Line Items]
Unrealized losses on derivatives	$ 4,600,000
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	1,600,000	$ 3,600,000	2,500,000
Derivative liability	5,500,000	$ 9,300,000	$ 15,000,000
Northwest Natural Gas Company [Member] | (Current Ratings) A/A3
Derivative [Line Items]
With Adequate Assurance Calls	0
Without Adequate Assurance Calls	0
Northwest Natural Gas Company [Member] | BBB/Baa1
Derivative [Line Items]
With Adequate Assurance Calls	0
Without Adequate Assurance Calls	0
Northwest Natural Gas Company [Member] | BBB/Baa2
Derivative [Line Items]
With Adequate Assurance Calls	0
Without Adequate Assurance Calls	0
Northwest Natural Gas Company [Member] | BBB-/Baa3
Derivative [Line Items]
With Adequate Assurance Calls	(840,000)
Without Adequate Assurance Calls	(840,000)
Northwest Natural Gas Company [Member] | Speculative
Derivative [Line Items]
With Adequate Assurance Calls	(2,179,000)
Without Adequate Assurance Calls	$ (1,910,000)

Environmental Matters (Details)

Environmental Matters (Details)	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Oregon [Member]
Site Contingency [Line Items]
Remediation Recovery Percentage	96.68%	96.68%	96.68%

Environmental Matters - Environ

Environmental Matters - Environmental Sites (Details) $ in Thousands	1 Months Ended			6 Months Ended
	Jul. 31, 2017USD ($)	Jan. 31, 2017USD ($)	May 31, 2012USD ($)	Jun. 30, 2019USD ($)propertyparty	Dec. 31, 2018USD ($)	Jun. 30, 2018USD ($)
Site Contingency [Line Items]
Current Liabilities				$ 17,578	$ 33,112	$ 14,496
Non-Current Liabilities				103,020	95,636	105,641
Gasco/Siltronic Sediments
Site Contingency [Line Items]
Current Liabilities				4,403	5,117	2,174
Non-Current Liabilities				44,374	44,351	45,330
Site Contingency, Environmental Remediation Costs Recognized				48,800
Gasco/Siltronic Sediments | Minimum [Member]
Site Contingency [Line Items]
Environmental Exit Costs, Anticipated Cost			$ 48,800
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				2,150	2,600	1,444
Non-Current Liabilities				5,645	6,273	3,871
Gasco/Siltronic Upland [Member]
Site Contingency [Line Items]
Current Liabilities				9,964	13,983	9,947
Non-Current Liabilities				42,672	44,830	45,578
Central Service Center [Member]
Site Contingency [Line Items]
Current Liabilities				10	10	25
Non-Current Liabilities				0	0	0
Front Street [Member]
Site Contingency [Line Items]
Current Liabilities				1,051	11,402	906
Non-Current Liabilities				10,150	3	10,683
Undiscounted environmental remediation expense	$ 10,500
Additional studies and design costs	$ 700
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	6 Months Ended
	Mar. 31, 2019	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Site Contingency [Line Items]
Regulatory Assets, Current		$ 46,688	$ 41,930	$ 41,092
Regulatory Assets, Noncurrent		$ 318,340	$ 371,786	$ 339,177
Remediation Non-recovery Percentage		3.32%	3.32%	3.32%
Annual tariff rider collection		$ 5,000
Annual insurance proceeds to apply against remediation costs		5,000
Total annual remediation expense and interest		$ 10,000
Environmental Earnings Test Reserve	$ 4,400
Oregon [Member]
Site Contingency [Line Items]
Remediation Recovery Percentage		96.68%	96.68%	96.68%
Front Street [Member] | Environmental costs [Member]
Site Contingency [Line Items]
Accrued site liabilities		$ 400	$ 400	$ 400
Northwest Natural Gas Company [Member]
Site Contingency [Line Items]
Regulatory Assets, Current		46,688	41,930	41,092
Regulatory Assets, Noncurrent		318,340	371,786	339,177
Northwest Natural Gas Company [Member] | Environmental costs [Member]
Site Contingency [Line Items]
Deferred costs and interest		43,222	41,883	46,862
Accrued site liabilities		120,226	128,369	119,712
Insurance proceeds and interest		(90,119)	(88,502)	(95,824)
Regulatory Assets		73,329	81,750	70,750
Regulatory Assets, Current		5,089	5,601	5,594
Regulatory Assets, Noncurrent		$ 68,240	$ 76,149	$ 65,156

Discontinued Operations (Detail

Discontinued Operations (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2019	Dec. 31, 2018
Disposal Group, Including Discontinued Operation, Classified Balance Sheet Disclosures [Abstract]
Discontinued operations - current assets	$ 14,001	$ 12,743	$ 14,001	$ 12,743		$ 13,269
Discontinued operations - total assets		12,700		12,700
Discontinued operations current liabilities	13,279	12,922	13,279	12,922		12,959
Discontinued Operation, Income Statement Disclosures [Abstract]
Loss from discontinued operations, net of tax	(956)	(659)	(1,173)	(1,133)
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	519	497	519	497		390
Inventories	756	646	756	646		685
Other current assets	183	413	183	413		333
Property, plant, and equipment	12,184	10,948	12,184	10,948		11,621
Less: Accumulated depreciation	6	6	6	6		7
Operating lease right of use asset	118	0	118	0		0
Other non-current assets	247	245	247	245		247
Discontinued operations - total assets	14,001	12,743	14,001	12,743		13,269
Accounts payable	1,230	572	1,230	572		873
Other current liabilities	296	436	296	436		307
Operating lease liabilities	113	0	113	0		0
Other non-current liabilities	11,640	11,914	11,640	11,914		11,779
Total discontinued operations liabilities	13,279	12,922	13,279	12,922		$ 12,959
Gill Ranch [Member] | Discontinued Operations, Held-for-sale [Member]
Discontinued Operation, Income Statement Disclosures [Abstract]
Revenues	1,748	1,006	3,469	2,083
Operations and maintenance	2,651	1,554	4,264	2,590
General taxes	60	346	119	680
Depreciation and amortization	106	108	212	218
Other expenses and interest	229		466	134
Other interest		(107)
Total expenses	3,046	1,901	5,061	3,622
Loss from discontinued operations before income tax	(1,298)	(895)	(1,592)	(1,539)
Income tax benefit	(342)	(236)	(419)	(406)
Loss from discontinued operations, net of tax	$ (956)	$ (659)	$ (1,173)	$ (1,133)
Loss from discontinued operations per share of common stock
Basic (in dollars per share)	$ (0.03)	$ (0.02)	$ (0.04)	$ (0.04)
Diluted (in dollars per share)	$ (0.03)	$ (0.02)	$ (0.04)	$ (0.04)
Transferred Subsidiaries - NW Natural Discontinued Operations [Member] | Discontinued Operations, Disposed of by Means Other than Sale [Member]
Disposal Group, Including Discontinued Operation, Classified Balance Sheet Disclosures [Abstract]
Cash		$ 433		$ 433
Accounts receivable		498		498
Receivables from affiliates		3,814		3,814
Inventories		646		646
Other current assets		482		482
Property, plant, and equipment		11,323		11,323
Less: Accumulated depreciation		213		213
Other investments		13,673		13,673
Other non-current assets		254		254
Discontinued operations - current assets		5,873		5,873
Discontinued operations - non-current assets		25,037		25,037
Discontinued operations - total assets		30,910		30,910
Accounts payable		971		971
Taxes accrued		30		30
Payables to affiliates		265		265
Other current liabilities		1,436		1,436
Deferred tax liabilities		(15,022)		(15,022)
Other non-current liabilities		12,004		12,004
Discontinued operations current liabilities		2,702		2,702
Discontinued operations non-current liabilities		(3,018)		(3,018)
Total discontinued operations liabilities		316		316
Discontinued Operation, Income Statement Disclosures [Abstract]
Revenues		1,065		2,198
Operations and maintenance		1,684		2,743
General taxes		356		703
Depreciation and amortization		165		282
Other expenses and interest				110
Other interest		(150)
Total expenses		2,055		3,838
Loss from discontinued operations before income tax		(990)		(1,640)
Income tax benefit		(263)		(436)
Loss from discontinued operations, net of tax		$ (727)		$ (1,204)
Gill Ranch [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Percent ownership	75.00%		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%		25.00%
Scenario, Forecast [Member] | Minimum [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from divestiture of businesses					$ 25,000
Scenario, Forecast [Member] | Maximum [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from divestiture of businesses					$ 26,500