Consolidated Statements of Comprehensive Income - USD ($) shares in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating revenues [Abstract]
Operating revenues	$ 860,400,000	$ 773,679,000	$ 746,372,000
Operating expenses:
Cost of gas	292,314,000	262,755,000	254,911,000
Operations and maintenance	204,227,000	180,129,000	178,191,000
Environmental remediation	9,938,000	9,691,000	12,337,000
General taxes	38,633,000	35,078,000	32,388,000
Depreciation and amortization	113,534,000	103,683,000	91,496,000
Other operating expenses	3,897,000	3,701,000	3,250,000
Total operating expenses	697,283,000	625,328,000	602,898,000
Income from operations	163,117,000	148,351,000	143,474,000
Other income (expense), net	(12,559,000)	(13,944,000)	(22,836,000)
Interest expense, net	44,486,000	43,052,000	42,685,000
Income before income taxes	106,072,000	91,355,000	77,953,000
Income tax expense	27,406,000	21,082,000	12,642,000
Net income from continuing operations	78,666,000	70,273,000	65,311,000
Income (loss) from discontinued operations, net of tax	0	6,508,000	(3,576,000)
Net income	78,666,000	76,781,000	61,735,000
Other comprehensive income (loss):
Change in employee benefit plan liability, net of taxes	593,000	(2,848,000)	(2,655,000)
Amortization of non-qualified employee benefit plan liability, net of taxes	905,000	679,000	476,000
Comprehensive income	80,164,000	74,612,000	59,556,000
Supplemental Income Statement Elements [Abstract]
Change in employee benefit plan liability, taxes	(219)	1,025	956
Amortization of non-qualified employee benefit plan liability, taxes	$ (320)	$ (244)	$ (172)
Average common shares outstanding:
Basic (in shares)	30,702	30,541	29,786
Diluted (in shares)	30,752	30,599	29,859
Earnings from continuing operations per share of common stock:
Basic (in dollars per share)	$ 2.56	$ 2.30	$ 2.19
Diluted (in dollars per share)	2.56	2.30	2.19
Earnings (loss) from discontinued operations per share of common stock:
Basic (in dollars per share)	0	0.21	(0.12)
Diluted (in dollars per share)	0	0.21	(0.12)
Earnings per share of common stock:
Basic (in dollars per share)	2.56	2.51	2.07
Diluted (in dollars per share)	$ 2.56	$ 2.51	$ 2.07
Utilities Operating Expense, Taxes	$ 34,740,000	$ 30,291,000	$ 30,325,000
Northwest Natural Gas Company [Member]
Operating revenues [Abstract]
Operating revenues	843,057,000	758,748,000	739,944,000
Operating expenses:
Cost of gas	292,538,000	262,980,000	255,135,000
Utility Operations and maintenance	188,762,000	168,869,000	169,091,000
Environmental remediation	9,938,000	9,691,000	12,337,000
General taxes	38,150,000	34,459,000	32,075,000
Depreciation and amortization	110,504,000	101,586,000	90,405,000
Other operating expenses	3,332,000	3,232,000	3,230,000
Total operating expenses	677,824,000	611,108,000	592,598,000
Income from operations	165,233,000	147,640,000	147,346,000
Other income (expense), net	(12,745,000)	(15,116,000)	(22,968,000)
Interest expense, net	42,983,000	40,866,000	41,339,000
Income before income taxes	109,505,000	91,658,000	83,039,000
Income tax expense	28,333,000	21,095,000	14,065,000
Net income	81,172,000	70,563,000	68,974,000
Other comprehensive income (loss):
Change in employee benefit plan liability, net of taxes	593,000	(2,848,000)	(2,655,000)
Amortization of non-qualified employee benefit plan liability, net of taxes	905,000	679,000	476,000
Comprehensive income	82,670,000	68,394,000	66,795,000
Supplemental Income Statement Elements [Abstract]
Change in employee benefit plan liability, taxes	(219)	1,025	956
Amortization of non-qualified employee benefit plan liability, taxes	(320)	(244)	(172)
Earnings per share of common stock:
Utilities Operating Expense, Taxes	$ 34,600,000	$ 30,291,000	$ 30,325,000