Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	$ 828,155	$ 744,366
Operating revenues	860,400	773,679	$ 746,372
Operating Lease, Lease Income	80	88
Natural Gas Distribution [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	783,027	710,422
Gas Storage Revenue, Net of Regulatory Sharing [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	10,830	9,759
Asset Management Revenue, Net of Regulatory Sharing [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	9,387	2,532
Appliance Center Revenue [Member] | Transferred at Point in Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	5,953	5,385
Other revenue [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	18,958	16,268
Alternative revenue [Member]
Disaggregation of Revenue [Line Items]
Operating revenues	14,694	10,870
Leasing revenue [Member]
Disaggregation of Revenue [Line Items]
Operating Lease, Lease Income	17,551	18,443
Operating Segments [Member] | Northwest Natural Gas Company [Member]
Disaggregation of Revenue [Line Items]
Operating revenues	843,057	758,748	739,944
Operating Segments [Member] | Natural Gas Distribution [Member]
Disaggregation of Revenue [Line Items]
Operating revenues	816,887	741,072	720,528
Corporate, Non-Segment [Member] | Other Northwest Natural [Member]
Disaggregation of Revenue [Line Items]
Operating revenues	26,170	17,676	19,416
Corporate, Non-Segment [Member] | Northwest Holdings Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	17,343	14,931
Operating revenues	17,343	14,931	6,428
Corporate, Non-Segment [Member] | Northwest Holdings Other [Member] | Natural Gas Distribution [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0
Corporate, Non-Segment [Member] | Northwest Holdings Other [Member] | Gas Storage Revenue, Net of Regulatory Sharing [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0
Corporate, Non-Segment [Member] | Northwest Holdings Other [Member] | Asset Management Revenue, Net of Regulatory Sharing [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0
Corporate, Non-Segment [Member] | Northwest Holdings Other [Member] | Appliance Center Revenue [Member] | Transferred at Point in Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0
Corporate, Non-Segment [Member] | Northwest Holdings Other [Member] | Other revenue [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	17,343	14,931
Corporate, Non-Segment [Member] | Northwest Holdings Other [Member] | Alternative revenue [Member]
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
Corporate, Non-Segment [Member] | Northwest Holdings Other [Member] | Leasing revenue [Member]
Disaggregation of Revenue [Line Items]
Operating Lease, Lease Income	0	0
Northwest Natural Gas Company [Member]
Disaggregation of Revenue [Line Items]
Operating revenues	843,057	758,748	$ 739,944
Northwest Natural Gas Company [Member] | Northwest Natural Gas Company [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	810,812	729,435
Operating revenues	843,057	758,748
Northwest Natural Gas Company [Member] | Northwest Natural Gas Company [Member] | Natural Gas Distribution [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	783,027	710,422
Northwest Natural Gas Company [Member] | Northwest Natural Gas Company [Member] | Gas Storage Revenue, Net of Regulatory Sharing [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	10,830	9,759
Northwest Natural Gas Company [Member] | Northwest Natural Gas Company [Member] | Asset Management Revenue, Net of Regulatory Sharing [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	9,387	2,532
Northwest Natural Gas Company [Member] | Northwest Natural Gas Company [Member] | Appliance Center Revenue [Member] | Transferred at Point in Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	5,953	5,385
Northwest Natural Gas Company [Member] | Northwest Natural Gas Company [Member] | Other revenue [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,615	1,337
Northwest Natural Gas Company [Member] | Northwest Natural Gas Company [Member] | Alternative revenue [Member]
Disaggregation of Revenue [Line Items]
Operating revenues	14,694	10,870
Northwest Natural Gas Company [Member] | Northwest Natural Gas Company [Member] | Leasing revenue [Member]
Disaggregation of Revenue [Line Items]
Operating Lease, Lease Income	17,551	18,443
Northwest Natural Gas Company [Member] | Operating Segments [Member] | Natural Gas Distribution [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	784,642	711,759
Operating revenues	816,887	741,072
Northwest Natural Gas Company [Member] | Operating Segments [Member] | Natural Gas Distribution [Member] | Natural Gas Distribution [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	783,027	710,422
Northwest Natural Gas Company [Member] | Operating Segments [Member] | Natural Gas Distribution [Member] | Gas Storage Revenue, Net of Regulatory Sharing [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0
Northwest Natural Gas Company [Member] | Operating Segments [Member] | Natural Gas Distribution [Member] | Asset Management Revenue, Net of Regulatory Sharing [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0
Northwest Natural Gas Company [Member] | Operating Segments [Member] | Natural Gas Distribution [Member] | Appliance Center Revenue [Member] | Transferred at Point in Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0
Northwest Natural Gas Company [Member] | Operating Segments [Member] | Natural Gas Distribution [Member] | Other revenue [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,615	1,337
Northwest Natural Gas Company [Member] | Operating Segments [Member] | Natural Gas Distribution [Member] | Alternative revenue [Member]
Disaggregation of Revenue [Line Items]
Operating revenues	14,694	10,870
Northwest Natural Gas Company [Member] | Operating Segments [Member] | Natural Gas Distribution [Member] | Leasing revenue [Member]
Disaggregation of Revenue [Line Items]
Operating Lease, Lease Income	17,551	18,443
Northwest Natural Gas Company [Member] | Corporate, Non-Segment [Member] | Other Northwest Natural [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	26,170	17,676
Operating revenues	26,170	17,676
Northwest Natural Gas Company [Member] | Corporate, Non-Segment [Member] | Other Northwest Natural [Member] | Natural Gas Distribution [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0
Northwest Natural Gas Company [Member] | Corporate, Non-Segment [Member] | Other Northwest Natural [Member] | Gas Storage Revenue, Net of Regulatory Sharing [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	10,830	9,759
Northwest Natural Gas Company [Member] | Corporate, Non-Segment [Member] | Other Northwest Natural [Member] | Asset Management Revenue, Net of Regulatory Sharing [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	9,387	2,532
Northwest Natural Gas Company [Member] | Corporate, Non-Segment [Member] | Other Northwest Natural [Member] | Appliance Center Revenue [Member] | Transferred at Point in Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	5,953	5,385
Northwest Natural Gas Company [Member] | Corporate, Non-Segment [Member] | Other Northwest Natural [Member] | Other revenue [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0
Northwest Natural Gas Company [Member] | Corporate, Non-Segment [Member] | Other Northwest Natural [Member] | Alternative revenue [Member]
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
Northwest Natural Gas Company [Member] | Corporate, Non-Segment [Member] | Other Northwest Natural [Member] | Leasing revenue [Member]
Disaggregation of Revenue [Line Items]
Operating Lease, Lease Income	$ 0	$ 0