Consolidated Statement of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating activities:
Net income		$ 76,781	$ 61,735	$ 64,569
Adjustments to reconcile net income to cash provided by operations:
Depreciation and amortization		103,683	91,496	85,156
Regulatory amortization of gas reserves		17,779	19,172	16,684
Deferred income taxes		18,667	6,317	14,356
Qualified defined benefit pension plan expense		18,370	16,497	8,108
Contributions to qualified defined benefit pension plans		(28,980)	(10,970)	(15,540)
Deferred environmental expenditures, net		(27,871)	(16,226)	(14,528)
Environmental remediation expense		9,691	12,337	11,127
Regulatory revenue deferral from the TCJA		0	853	7,929
Regulatory disallowance of pension costs		0	10,500	0
Gain on sale of discontinued operations, net of tax		(5,902)	0	0
Other		6,942	(13,907)	(1,596)
Changes in assets and liabilities:
Receivables, net		(16,799)	5,844	181
Inventories		1,262	(5,969)	3,207
Income and other taxes		(10,710)	4,528	(16,904)
Accounts payable		(15,910)	(16,485)	16,792
Deferred gas costs		17,590	(23,471)	(14,395)
Decoupling mechanism		2,884	18,661	4,497
Other, net		(12,467)	(4,140)	(3,419)
Discontinued operations		1,894	712	(645)
Cash provided by operating activities		143,020	185,298	168,771
Investing activities:
Capital expenditures		(273,016)	(223,471)	(214,636)
Acquisitions, net of cash acquired		(38,263)	(56,786)	(873)
Leasehold improvement expenditures		(7,878)	(18,812)	(4,415)
Proceeds from the sale of assets		8,149	659	477
Proceeds from Sale of Equity Method Investments		7,000	0	0
Proceeds from sale of discontinued operations		12,500	0	0
Other		1,654	(3,544)	1,421
Discontinued operations		(4,423)	(1,827)	573
Cash used in investing activities		(294,277)	(303,781)	(217,453)
Financing activities:
Proceeds from stock options exercised		68	2,015	1,546
Proceeds from common stock issued		0	92,956	0
Long-term debt issued		150,000	175,000	50,000
Long-term debt retired		(75,000)	(30,000)	(97,000)
Repayments of Short-term Debt		(150,000)	0	0
Proceeds from issuances of commercial paper, maturities greater than 90 days		195,025	0	0
Changes in other short-term debt, net		(39,600)	(68,520)	163,274
Cash dividend payments on common stock		(55,420)	(53,339)	(51,311)
Stock purchases related to acquisitions		0	0	(7,951)
Other		(3,296)	(2,614)	(715)
Cash provided by financing activities		171,777	115,498	57,843
Increase (decrease) in cash and cash equivalents		20,520	(2,985)	9,161
Cash and cash equivalents, beginning of period	$ 30,168	9,648	12,633	3,472
Cash and cash equivalents, end of period		30,168	9,648	12,633
Supplemental disclosure of cash flow information:
Interest paid, net of capitalization		42,651	41,231	35,324
Income taxes paid (refunded)		13,644	(96)	27,370
Proceeds from Debt, Maturing in More than Three Months		150,000	0	0
Forecast [Member]
Investing activities:
Proceeds from Sale of Equity Method Investments	14,000
Northwest Natural Gas Company [Member]
Operating activities:
Net income		70,563	68,974	66,326
Adjustments to reconcile net income to cash provided by operations:
Depreciation and amortization		101,586	90,405	84,986
Regulatory amortization of gas reserves		17,779	19,172	16,684
Deferred income taxes		4,645	4,046	12,330
Qualified defined benefit pension plan expense		18,370	16,497	8,108
Contributions to qualified defined benefit pension plans		(28,980)	(10,970)	(15,540)
Deferred environmental expenditures, net		(27,871)	(16,226)	(14,528)
Environmental remediation expense		9,691	12,337	11,127
Regulatory revenue deferral from the TCJA		0	853	7,929
Regulatory disallowance of pension costs		0	10,500	0
Other		7,025	(12,317)	(883)
Changes in assets and liabilities:
Receivables, net		(16,540)	9,264	(3,920)
Inventories		1,539	(5,990)	3,212
Income and other taxes		10,832	496	(7,854)
Accounts payable		(18,909)	(18,548)	13,937
Deferred gas costs		17,590	(23,471)	(14,395)
Decoupling mechanism		2,884	18,661	4,497
Other, net		(9,935)	(2,141)	(3,458)
Discontinued operations		0	0	3,184
Cash provided by operating activities		146,219	186,176	173,508
Investing activities:
Capital expenditures		(266,048)	(221,380)	(214,328)
Leasehold improvement expenditures		(7,878)	(18,812)	(4,415)
Proceeds from the sale of assets		8,149	659	477
Other		1,654	(3,544)	421
Discontinued operations		0	0	(20,617)
Cash used in investing activities		(264,123)	(243,077)	(238,462)
Financing activities:
Proceeds from stock options exercised		0	0	1,368
Long-term debt issued		150,000	140,000	50,000
Long-term debt retired		(75,000)	(30,000)	(97,000)
Repayments of Short-term Debt		(150,000)	0	0
Proceeds from issuances of commercial paper, maturities greater than 90 days		195,025	0	0
Changes in other short-term debt, net		(88,600)	(92,400)	163,300
Cash contributions received from parent		0	93,155	0
Cash dividend payments on common stock		(55,355)	(53,372)	(38,387)
Other		(3,632)	(2,510)	(1,539)
Discontinued operations		0	0	(7,951)
Cash provided by financing activities		122,438	54,873	69,791
Increase (decrease) in cash and cash equivalents		4,534	(2,028)	4,837
Cash and cash equivalents, beginning of period	$ 10,453	5,919	7,947	3,110
Cash and cash equivalents, end of period		10,453	5,919	7,947
Supplemental disclosure of cash flow information:
Interest paid, net of capitalization		40,624	39,927	35,305
Income taxes paid (refunded)		6,100	2,479	27,350
Proceeds from Debt, Maturing in More than Three Months		$ 150,000	$ 0	$ 0