Consolidated Statement of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating activities:
Net income	$ 78,666	$ 76,781	$ 61,735
Adjustments to reconcile net income to cash provided by operations:
Depreciation and amortization	113,534	103,683	91,496
Regulatory amortization of gas reserves	13,897	17,779	19,172
Deferred income taxes	14,617	18,667	6,317
Qualified defined benefit pension plan expense	16,556	18,370	16,497
Contributions to qualified defined benefit pension plans	(9,590)	(28,980)	(10,970)
Deferred environmental expenditures, net	(18,187)	(27,871)	(16,226)
Environmental remediation expense	9,938	9,691	12,337
Regulatory disallowance of pension costs	0	0	10,500
Gain on sale of discontinued operations, net of tax	0	(5,902)	0
Other	11,569	(6,942)	14,760
Changes in assets and liabilities:
Receivables, net	(44,128)	(16,799)	5,844
Inventories	(14,571)	1,262	(5,969)
Income and other taxes	3,292	(10,710)	4,528
Accounts payable	12,118	(15,910)	(16,485)
Deferred gas costs	(40,541)	17,590	(23,471)
Decoupling mechanism	44,458	(7,244)	655
Other, net	(26,069)	(2,925)	(4,080)
Discontinued operations	0	1,894	712
Cash provided by operating activities	160,353	145,318	186,013
Investing activities:
Capital expenditures	(293,892)	(273,016)	(223,471)
Acquisitions, net of cash acquired	(1,289)	(38,263)	(56,786)
Leasehold improvement expenditures	(1,364)	(7,878)	(18,812)
Proceeds from the sale of assets	3,926	8,149	659
Payments to Acquire Equity Method Investments	(14,450)	0	0
Proceeds from Sale of Equity Method Investments	7,000	7,000	0
Proceeds from sale of discontinued operations	0	12,500	0
Other	(54)	1,654	(3,544)
Discontinued operations	0	(4,423)	(1,827)
Cash used in investing activities	(300,123)	(294,277)	(303,781)
Financing activities:
Proceeds from common stock issued, net	17,501	0	92,956
Long-term debt issued	185,000	150,000	175,000
Long-term debt retired	(95,000)	(75,000)	(30,000)
Repayments of Short-term Debt	(100,000)	(150,000)	0
Proceeds from issuances of commercial paper, maturities greater than 90 days	0	195,025	0
Repayments of commercial paper, maturities greater than three months	(195,025)	0	0
Changes in other short-term debt, net	280,000	(39,600)	(68,520)
Cash dividend payments on common stock	(55,919)	(55,420)	(53,339)
Other	(5,121)	(3,228)	(599)
Cash provided by financing activities	131,436	171,777	115,498
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Excluding Exchange Rate Effect, Total	(8,334)	22,818	(2,270)
Cash, cash equivalents and restricted cash, beginning of period	30,168
Cash, cash equivalents and restricted cash, end of period	18,559	30,168
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	27,120	35,454	12,636
Supplemental disclosure of cash flow information:
Interest paid, net of capitalization	43,719	42,651	41,231
Income taxes paid (refunded)	10,555	13,644	(96)
Proceeds from Debt, Maturing in More than Three Months	100,000	150,000	0
Change In Decoupling Regulatory Deferral	(5,206)	2,884	18,661
Northwest Natural Gas Company [Member]
Operating activities:
Net income	81,172	70,563	68,974
Adjustments to reconcile net income to cash provided by operations:
Depreciation and amortization	110,504	101,586	90,405
Regulatory amortization of gas reserves	13,897	17,779	19,172
Deferred income taxes	13,223	4,645	4,046
Qualified defined benefit pension plan expense	16,556	18,370	16,497
Contributions to qualified defined benefit pension plans	(9,590)	(28,980)	(10,970)
Deferred environmental expenditures, net	(18,187)	(27,871)	(16,226)
Environmental remediation expense	9,938	9,691	12,337
Regulatory disallowance of pension costs	0	0	10,500
Other	9,464	(7,025)	13,170
Changes in assets and liabilities:
Receivables, net	(43,030)	(16,540)	9,264
Inventories	(14,427)	1,539	(5,990)
Income and other taxes	(10,405)	10,832	496
Accounts payable	8,728	(18,909)	(18,548)
Deferred gas costs	(40,541)	17,590	(23,471)
Decoupling mechanism	44,458	(7,244)	655
Other, net	(25,060)	(393)	(2,081)
Cash provided by operating activities	141,494	148,517	186,891
Investing activities:
Capital expenditures	(278,237)	(266,048)	(221,380)
Leasehold improvement expenditures	(1,364)	(7,878)	(18,812)
Proceeds from the sale of assets	3,926	8,149	659
Other	(54)	1,654	(3,544)
Cash used in investing activities	(275,729)	(264,123)	(243,077)
Financing activities:
Long-term debt issued	130,000	150,000	140,000
Long-term debt retired	(60,000)	(75,000)	(30,000)
Repayments of Short-term Debt	(100,000)	(150,000)	0
Proceeds from issuances of commercial paper, maturities greater than 90 days	0	195,025	0
Repayments of commercial paper, maturities greater than three months	(195,025)	0	0
Changes in other short-term debt, net	209,000	(88,600)	(92,400)
Cash contributions received from parent	116,009	0	93,155
Cash dividend payments on common stock	(56,056)	(55,355)	(53,372)
Other	(4,600)	(3,632)	(2,510)
Cash provided by financing activities	139,328	122,438	54,873
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Excluding Exchange Rate Effect, Total	5,093	6,832	(1,313)
Cash, cash equivalents and restricted cash, beginning of period	10,453
Cash, cash equivalents and restricted cash, end of period	12,271	10,453
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	20,832	15,739	8,907
Supplemental disclosure of cash flow information:
Interest paid, net of capitalization	42,395	40,624	39,927
Income taxes paid (refunded)	26,451	6,100	2,479
Proceeds from Debt, Maturing in More than Three Months	100,000	150,000	0
Change In Decoupling Regulatory Deferral	$ (5,206)	$ 2,884	$ 18,661