Consolidated Statement of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Operating activities:
Net income	$ 86,303	$ 78,666	$ 76,781
Adjustments to reconcile net income to cash provided by operations:
Depreciation	116,707	113,534	103,683
Regulatory amortization of gas reserves	5,589	13,897	17,779
Deferred income taxes	17,410	14,617	18,667
Qualified defined benefit pension plan expense	5,351	16,556	18,370
Contributions to qualified defined benefit pension plans	0	(9,590)	(28,980)
Deferred environmental expenditures, net	(18,160)	(18,187)	(27,871)
Environmental remediation expense	12,389	9,938	9,691
Gain on sale of discontinued operations, net of tax	0	0	(5,902)
Asset optimization revenue sharing bill credits	(41,102)	(9,053)	(16,970)
Other	21,558	20,622	10,028
Changes in assets and liabilities:
Receivables, net	(76,454)	(44,128)	(16,799)
Inventories	(29,269)	(14,571)	1,262
Income and other taxes	6,908	3,292	(10,710)
Accounts payable	24,508	12,118	(15,910)
Deferred gas costs	12,334	(40,541)	17,590
Asset optimization revenue sharing	28,937	44,458	(7,244)
Decoupling mechanism	10,922	(5,206)	2,884
Cloud-based software	(23,908)	(7,407)	(4,265)
Other, net	(12,351)	(18,662)	1,340
Discontinued operations	0	0	1,894
Cash provided by operating activities	147,672	160,353	145,318
Investing activities:
Capital expenditures	(338,602)	(293,892)	(273,016)
Acquisitions, net of cash acquired	(94,279)	(1,289)	(38,263)
Leasehold improvement expenditures	(761)	(1,364)	(7,878)
Proceeds from the sale of assets	870	3,926	8,149
Purchase of equity method investment	(1,000)	(14,450)	0
Proceeds from Sale of Equity Method Investments	0	7,000	7,000
Proceeds from sale of discontinued operations	0	0	12,500
Other	(1,688)	(54)	1,654
Discontinued operations	0	0	(4,423)
Cash used in investing activities	(435,460)	(300,123)	(294,277)
Financing activities:
Proceeds from common stock issued, net	208,561	17,501	0
Long-term debt issued	290,000	185,000	150,000
Long-term debt retired	0	(95,000)	(75,000)
Proceeds from term loan due within one year	0	100,000	150,000
Repayments of Short-term Debt	0	(100,000)	(150,000)
Proceeds from commercial paper, maturities greater than three months	0	0	195,025
Repayments of commercial paper, maturities greater than three months	0	(195,025)	0
Changes in other short-term debt, net	(131,300)	280,000	(39,600)
Cash dividend payments on common stock	(62,771)	(55,919)	(55,420)
Other	(2,858)	(5,121)	(3,228)
Cash provided by financing activities	301,632	131,436	171,777
Increase (decrease) in cash, cash equivalents and restricted cash	13,844	(8,334)	22,818
Cash, cash equivalents and restricted cash, beginning of period	18,559
Cash, cash equivalents and restricted cash, end of period	29,270	18,559
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	40,964	27,120	35,454
Supplemental disclosure of cash flow information:
Interest paid, net of capitalization	50,823	43,719	42,651
Income taxes paid, net of refunds	2,779	10,555	13,644
Northwest Natural Gas Company [Member]
Operating activities:
Net income	91,564	81,172	70,563
Adjustments to reconcile net income to cash provided by operations:
Depreciation	112,957	110,504	101,586
Regulatory amortization of gas reserves	5,589	13,897	17,779
Deferred income taxes	16,288	13,223	4,645
Qualified defined benefit pension plan expense	5,351	16,556	18,370
Contributions to qualified defined benefit pension plans	0	(9,590)	(28,980)
Deferred environmental expenditures, net	(18,160)	(18,187)	(27,871)
Environmental remediation expense	12,389	9,938	9,691
Asset optimization revenue sharing bill credits	(41,102)	(9,053)	(16,970)
Other	20,448	18,517	9,945
Changes in assets and liabilities:
Receivables, net	(75,177)	(43,030)	(16,540)
Inventories	(28,890)	(14,427)	1,539
Income and other taxes	6,729	(10,405)	10,832
Accounts payable	21,375	8,728	(18,909)
Deferred gas costs	12,334	(40,541)	17,590
Asset optimization revenue sharing	28,937	44,458	(7,244)
Decoupling mechanism	10,922	(5,206)	2,884
Cloud-based software	(23,908)	(7,407)	(4,265)
Other, net	(12,455)	(17,653)	3,872
Cash provided by operating activities	145,191	141,494	148,517
Investing activities:
Capital expenditures	(318,686)	(278,237)	(266,048)
Leasehold improvement expenditures	(761)	(1,364)	(7,878)
Proceeds from the sale of assets	870	3,926	8,149
Other	(1,688)	(54)	1,654
Cash used in investing activities	(320,265)	(275,729)	(264,123)
Financing activities:
Long-term debt issued	140,000	130,000	150,000
Long-term debt retired	0	(60,000)	(75,000)
Proceeds from term loan due within one year	0	100,000	150,000
Repayments of Short-term Debt	0	(100,000)	(150,000)
Proceeds from commercial paper, maturities greater than three months	0	0	195,025
Repayments of commercial paper, maturities greater than three months	0	(195,025)	0
Changes in other short-term debt, net	(75,300)	209,000	(88,600)
Cash contributions received from parent	179,388	116,009	0
Cash dividend payments on common stock	(62,667)	(56,056)	(55,355)
Other	(2,508)	(4,600)	(3,632)
Cash provided by financing activities	178,913	139,328	122,438
Increase (decrease) in cash, cash equivalents and restricted cash	3,839	5,093	6,832
Cash, cash equivalents and restricted cash, beginning of period	12,271
Cash, cash equivalents and restricted cash, end of period	12,977	12,271
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	24,671	20,832	15,739
Supplemental disclosure of cash flow information:
Interest paid, net of capitalization	44,813	42,395	40,624
Income taxes paid, net of refunds	$ 5,990	$ 26,451	$ 6,100