Consolidated Statements of Comprehensive Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Operating revenues [Abstract]
Operating revenues	$ 194,960	$ 148,917	$ 545,261	$ 464,863
Operating expenses:
Cost of gas	79,720	41,193	225,308	153,403
Operations and maintenance	53,175	50,047	110,660	102,238
Environmental remediation	2,267	1,509	6,970	5,286
General taxes	8,989	8,914	21,093	20,283
Revenue taxes	8,240	5,671	21,600	18,335
Depreciation	28,110	28,144	56,539	56,241
Other operating expenses	920	815	1,914	1,747
Total operating expenses	181,421	136,293	444,084	357,533
Income from operations	13,539	12,624	101,177	107,330
Other income (expense), net	226	(2,597)	(728)	(6,139)
Interest expense, net	11,580	11,028	23,102	22,154
Income (loss) before income taxes	2,185	(1,001)	77,347	79,037
Income tax expense (benefit)	470	(277)	19,393	20,244
Net income (loss)	1,715	(724)	57,954	58,793
Other comprehensive income:
Amortization of non-qualified employee benefit plan liability, net of taxes	197	221	394	442
Comprehensive income (loss)	1,912	(503)	58,348	59,235
Supplemental Income Statement Elements [Abstract]
Amortization of non-qualified employee benefit plan liability, tax	$ 71	$ 80	$ 142	$ 160
Average common shares outstanding:
Basic (in shares)	34,307	30,664	32,756	30,639
Diluted (in shares)	34,352	30,664	32,805	30,671
Earnings per share of common stock:
Basic (in dollars per share)	$ 0.05	$ (0.02)	$ 1.77	$ 1.92
Diluted (in dollars per share)	$ 0.05	$ (0.02)	$ 1.77	$ 1.92
Northwest Natural Gas Company [Member]
Operating revenues [Abstract]
Operating revenues	$ 190,251	$ 144,579	$ 536,875	$ 456,929
Operating expenses:
Cost of gas	79,776	41,249	225,420	153,515
Operations and maintenance	48,879	44,939	102,756	94,126
Environmental remediation	2,267	1,509	6,970	5,286
General taxes	8,872	8,783	20,861	20,042
Revenue taxes	8,208	5,650	21,532	18,305
Depreciation	27,328	27,530	54,965	54,699
Other operating expenses	796	780	1,695	1,699
Total operating expenses	176,126	130,440	434,199	347,672
Income from operations	14,125	14,139	102,676	109,257
Other income (expense), net	17	(2,566)	(964)	(6,231)
Interest expense, net	10,599	10,696	21,430	21,486
Income (loss) before income taxes	3,543	877	80,282	81,540
Income tax expense (benefit)	810	288	20,133	20,840
Net income (loss)	2,733	589	60,149	60,700
Other comprehensive income:
Amortization of non-qualified employee benefit plan liability, net of taxes	197	221	394	442
Comprehensive income (loss)	2,930	810	60,543	61,142
Supplemental Income Statement Elements [Abstract]
Amortization of non-qualified employee benefit plan liability, tax	$ 71	$ 80	$ 142	$ 160