Consolidated Statements of Comprehensive Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Operating revenues [Abstract]
Operating revenues	$ 123,443	$ 124,567	$ 408,791	$ 388,202
Operating expenses:
Cost of gas	35,107	42,053	140,564	150,159
Operations and maintenance	39,486	38,028	90,968	77,551
Environmental remediation	(2,656)	1,882	6,291	6,506
General taxes	7,879	7,729	16,906	17,203
Revenue taxes	4,496	4,780	16,422	17,209
Depreciation and amortization	22,387	21,147	43,959	42,022
Other operating expenses	646	679	1,538	1,532
Total operating expenses	107,345	116,298	316,648	312,182
Income from operations	16,098	8,269	92,143	76,020
Other income (expense), net	(2,768)	7	(16,515)	(827)
Interest expense, net	10,654	8,771	20,859	18,045
Income before income taxes	2,676	(495)	54,769	57,148
Income tax expense	625	(156)	9,300	15,476
Net income from continuing operations	2,051	(339)	45,469	41,672
Loss from discontinued operations, net of tax	(956)	(659)	(1,173)	(1,133)
Net income (loss)	1,095	(998)	44,296	40,539
Other comprehensive income:
Amortization of non-qualified employee benefit plan liability, net of taxes	115	153	230	307
Comprehensive income (loss)	$ 1,210	$ (845)	$ 44,526	$ 40,846
Average common shares outstanding:
Basic (in shares)	29,337	28,791	29,123	28,772
Diluted (in shares)	29,394	28,791	29,186	28,825
Earnings from continuing operations per share of common stock:
Basic (in dollars per share)	$ 0.07	$ (0.01)	$ 1.56	$ 1.45
Diluted (in dollars per share)	0.07	(0.01)	1.56	1.45
Earnings (loss) per share of common stock:
Basic (in dollars per share)	0.04	(0.03)	1.52	1.41
Diluted (in dollars per share)	$ 0.04	$ (0.03)	$ 1.52	$ 1.41
Northwest Natural Gas Company [Member]
Operating revenues [Abstract]
Operating revenues	$ 122,242	$ 124,563	$ 407,088	$ 388,198
Operating expenses:
Cost of gas	35,163	42,107	140,676	150,271
Operations and maintenance	37,292	37,899	87,726	77,399
Environmental remediation	(2,656)	1,882	6,291	6,506
General taxes	7,826	7,721	16,814	17,180
Revenue taxes	4,496	4,780	16,422	17,209
Depreciation and amortization	22,243	21,090	43,747	41,958
Other operating expenses	638	679	1,528	1,532
Total operating expenses	105,002	116,158	313,204	312,055
Income from operations	17,240	8,405	93,884	76,143
Other income (expense), net	(2,814)	(33)	(16,582)	(848)
Interest expense, net	10,387	8,771	20,520	18,045
Income before income taxes	4,039	(399)	56,782	57,250
Income tax expense	985	(128)	9,833	15,507
Net income from continuing operations	3,054	(271)	46,949	41,743
Loss from discontinued operations, net of tax	0	(727)	0	(1,204)
Net income (loss)	3,054	(998)	46,949	40,539
Other comprehensive income:
Amortization of non-qualified employee benefit plan liability, net of taxes	115	153	230	307
Comprehensive income (loss)	$ 3,169	$ (845)	$ 47,179	$ 40,846