Consolidated Statements of Comprehensive Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Operating revenues [Abstract]
Operating revenues	$ 90,317	$ 91,239	$ 499,108	$ 479,441
Operating expenses:
Cost of gas	22,603	25,538	163,167	175,697
Operations and maintenance	40,886	37,569	131,854	115,120
Environmental remediation	967	1,022	7,258	7,528
General taxes	7,993	7,589	24,899	24,792
Revenue taxes	3,534	3,522	19,956	20,731
Depreciation and amortization	23,375	21,485	67,334	63,507
Other operating expenses	593	625	2,131	2,157
Total operating expenses	99,951	97,350	416,599	409,532
Income from operations	(9,634)	(6,111)	82,509	69,909
Other income (expense), net	(2,267)	(312)	(18,782)	(1,139)
Interest expense, net	10,948	9,006	31,807	27,051
Income before income taxes	(22,849)	(15,429)	31,920	41,719
Income tax expense	(4,343)	(4,285)	4,957	11,191
Net income from continuing operations	(18,506)	(11,144)	26,963	30,528
Loss from discontinued operations, net of tax	(795)	(650)	(1,968)	(1,783)
Net income (loss)	(19,301)	(11,794)	24,995	28,745
Other comprehensive income:
Amortization of non-qualified employee benefit plan liability, net of taxes	114	154	344	461
Comprehensive income (loss)	$ (19,187)	$ (11,640)	$ 25,339	$ 29,206
Average common shares outstanding:
Basic (in shares)	30,429	28,815	29,563	28,787
Diluted (in shares)	30,429	28,815	29,628	28,846
Earnings from continuing operations per share of common stock:
Basic (in dollars per share)	$ (0.61)	$ (0.39)	$ 0.91	$ 1.06
Diluted (in dollars per share)	(0.61)	(0.39)	0.91	1.06
Loss from discontinued operations per share of common stock:
Basic (in dollars per share)	(0.02)	(0.02)	(0.07)	(0.06)
Diluted (in dollars per share)	(0.02)	(0.02)	(0.07)	(0.06)
Earnings (loss) per share of common stock:
Basic (in dollars per share)	(0.63)	(0.41)	0.84	1.00
Diluted (in dollars per share)	$ (0.63)	$ (0.41)	$ 0.84	$ 1.00
Northwest Natural Gas Company [Member]
Operating revenues [Abstract]
Operating revenues	$ 87,592	$ 91,227	$ 494,680	$ 479,425
Operating expenses:
Cost of gas	22,659	25,593	163,335	175,864
Operations and maintenance	37,710	37,709	125,436	115,108
Environmental remediation	967	1,022	7,258	7,528
General taxes	7,881	7,584	24,695	24,764
Revenue taxes	3,534	3,522	19,956	20,731
Depreciation and amortization	23,074	21,454	66,821	63,412
Other operating expenses	586	624	2,114	2,156
Total operating expenses	96,411	97,508	409,615	409,563
Income from operations	(8,819)	(6,281)	85,065	69,862
Other income (expense), net	(2,323)	(320)	(18,905)	(1,168)
Interest expense, net	10,459	9,007	30,979	27,052
Income before income taxes	(21,601)	(15,608)	35,181	41,642
Income tax expense	(4,013)	(4,333)	5,820	11,174
Net income from continuing operations	(17,588)	(11,275)	29,361	30,468
Loss from discontinued operations, net of tax	0	(519)	0	(1,723)
Net income (loss)	(17,588)	(11,794)	29,361	28,745
Other comprehensive income:
Amortization of non-qualified employee benefit plan liability, net of taxes	114	154	344	461
Comprehensive income (loss)	$ (17,474)	$ (11,640)	$ 29,705	$ 29,206