Consolidated Statement of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Operating activities:
Net income	$ 58,793	$ 42,646
Adjustments to reconcile net income to cash provided by operations:
Depreciation and amortization	56,241	50,511
Regulatory amortization of gas reserves	7,597	8,567
Deferred income taxes	1,048	(2,004)
Qualified defined benefit pension plan expense	7,874	8,892
Contributions to qualified defined benefit pension plans	(9,590)	(8,470)
Deferred environmental expenditures, net	(9,625)	(9,897)
Amortization of environmental remediation	5,286	5,627
Other	1,610	(5,931)
Changes in assets and liabilities:
Receivables, net	73,133	73,954
Inventories	3,666	(52)
Income and other taxes	21,467	20,966
Accounts payable	(17,239)	(18,919)
Deferred gas costs	(26,962)	115
Asset optimization revenue sharing	36,872	(11,657)
Decoupling mechanism	(6,860)	4,281
Other, net	(9,030)	3,967
Discontinued operations	0	(547)
Cash provided by operating activities	194,281	162,049
Investing activities:
Capital expenditures	(130,108)	(122,282)
Acquisitions, net of cash acquired	(55)	(37,940)
Leasehold improvement expenditures	(163)	(7,519)
Proceeds from the sale of assets	2,234	7,905
Other	209	263
Discontinued operations	0	(846)
Cash used in investing activities	(127,883)	(160,419)
Financing activities:
Proceeds from common stock issued	0	68
Long-term debt issued	55,000	150,000
Long-term debt retired	(35,000)	(75,000)
Proceeds from term loan due within one year	100,000	150,000
Repayments of commercial paper, maturities greater than 90 days	(195,025)	0
Proceeds from (Repayments of) Short-term Debt	30,500	(66,100)
Cash dividend payments on common stock	(27,842)	(27,679)
Other	(1,175)	(3,007)
Net Cash Provided by (Used in) Financing Activities	(73,542)	128,282
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	28,310	142,548
Increase in cash and cash equivalents	(7,144)	129,912
Supplemental disclosure of cash flow information:
Interest paid, net of capitalization	21,971	23,156
Income taxes paid, net of refunds	7,405	544
Northwest Natural Gas Company [Member]
Operating activities:
Net income	60,700	44,467
Adjustments to reconcile net income to cash provided by operations:
Depreciation and amortization	54,699	49,176
Regulatory amortization of gas reserves	7,597	8,567
Deferred income taxes	201	(2,766)
Qualified defined benefit pension plan expense	7,874	8,892
Contributions to qualified defined benefit pension plans	(9,590)	(8,470)
Deferred environmental expenditures, net	(9,625)	(9,897)
Amortization of environmental remediation	5,286	5,627
Other	481	(6,746)
Changes in assets and liabilities:
Receivables, net	74,354	74,625
Inventories	3,775	249
Income and other taxes	19,440	22,038
Accounts payable	(19,936)	(22,186)
Deferred gas costs	(26,962)	115
Asset optimization revenue sharing	36,872	(11,657)
Decoupling mechanism	(6,860)	4,281
Other, net	(8,361)	5,979
Cash provided by operating activities	189,945	162,294
Investing activities:
Capital expenditures	(125,167)	(118,227)
Leasehold improvement expenditures	(163)	(7,519)
Proceeds from the sale of assets	2,234	7,905
Other	209	269
Cash used in investing activities	(122,887)	(117,572)
Financing activities:
Long-term debt issued	0	150,000
Long-term debt retired	0	(75,000)
Proceeds from term loan due within one year	100,000	150,000
Repayments of commercial paper, maturities greater than 90 days	(195,025)	0
Proceeds from (Repayments of) Short-term Debt	61,500	(122,100)
Cash dividend payments on common stock	(27,935)	(27,614)
Other	(1,623)	(3,140)
Net Cash Provided by (Used in) Financing Activities	(63,083)	72,146
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	19,714	125,775
Increase in cash and cash equivalents	3,975	116,868
Supplemental disclosure of cash flow information:
Interest paid, net of capitalization	21,285	21,794
Income taxes paid, net of refunds	$ 10,910	$ 950