Consolidated Statements of Comprehensive Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Operating revenues [Abstract]
Operating revenues	$ 134,971	$ 123,443	$ 420,122	$ 408,791
Operating expenses:
Cost of gas	41,210	35,107	149,748	140,564
Operations and maintenance	43,983	39,486	92,904	90,968
Environmental remediation	1,622	(2,656)	5,627	6,291
General taxes	8,373	7,879	18,268	16,906
Revenue taxes	4,454	4,496	16,197	16,422
Depreciation and amortization	25,836	22,387	50,511	43,959
Other operating expenses	551	646	1,479	1,538
Total operating expenses	126,029	107,345	334,734	316,648
Income from operations	8,942	16,098	85,388	92,143
Other income (expense), net	(3,040)	(2,768)	(6,615)	(16,515)
Interest expense, net	12,706	10,654	23,174	20,859
Income (loss) before income taxes	(6,804)	2,676	55,599	54,769
Income tax expense (benefit)	(1,672)	625	12,455	9,300
Net income (loss) from continuing operations	(5,132)	2,051	43,144	45,469
Income (loss) from discontinued operations, net of tax	280	(956)	(498)	(1,173)
Net income (loss)	(4,852)	1,095	42,646	44,296
Other comprehensive income:
Amortization of non-qualified employee benefit plan liability, net of taxes	160	115	320	230
Comprehensive income (loss)	$ (4,692)	$ 1,210	$ 42,966	$ 44,526
Average common shares outstanding:
Basic (in shares)	30,537	29,337	30,514	29,123
Diluted (in shares)	30,537	29,394	30,559	29,186
Earnings from continuing operations per share of common stock:
Basic (in dollars per share)	$ (0.17)	$ 0.07	$ 1.41	$ 1.56
Diluted (in dollars per share)	(0.17)	0.07	1.41	1.56
Loss from discontinued operations per share of common stock:
Basic (in dollars per share)	0.01	(0.03)	(0.01)	(0.04)
Diluted (in dollars per share)	0.01	(0.03)	(0.01)	(0.04)
Earnings (loss) per share of common stock:
Basic (in dollars per share)	(0.16)	0.04	1.40	1.52
Diluted (in dollars per share)	$ (0.16)	$ 0.04	$ 1.40	$ 1.52
Northwest Natural Gas Company [Member]
Operating revenues [Abstract]
Operating revenues	$ 131,157	$ 122,242	$ 413,686	$ 407,088
Operating expenses:
Cost of gas	41,265	35,163	149,860	140,676
Operations and maintenance	41,198	37,292	87,454	87,726
Environmental remediation	1,622	(2,656)	5,627	6,291
General taxes	8,211	7,826	18,010	16,814
Revenue taxes	4,454	4,496	16,197	16,422
Depreciation and amortization	24,986	22,243	49,176	43,747
Other operating expenses	522	638	1,442	1,528
Total operating expenses	122,258	105,002	327,766	313,204
Income from operations	8,899	17,240	85,920	93,884
Other income (expense), net	(3,179)	(2,814)	(6,742)	(16,582)
Interest expense, net	11,851	10,387	21,712	20,520
Income (loss) before income taxes	(6,131)	4,039	57,466	56,782
Income tax expense (benefit)	(1,419)	985	12,999	9,833
Net income (loss)	(4,712)	3,054	44,467	46,949
Other comprehensive income:
Amortization of non-qualified employee benefit plan liability, net of taxes	160	115	320	230
Comprehensive income (loss)	$ (4,552)	$ 3,169	$ 44,787	$ 47,179