Segment Information - Additional Segment Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Segment Reporting Information [Line Items]
Operating revenues	$ 1,197,475	$ 1,037,353	$ 860,400
Cost of gas	499,837	429,635	292,314
Environmental remediation	12,899	12,389	9,938
Revenue taxes	48,700	41,800	34,700
Northwest Natural Gas Company [Member]
Segment Reporting Information [Line Items]
Operating revenues	1,158,623	1,014,339	843,057
Cost of gas	500,061	429,861	292,538
Environmental remediation	$ 12,899	12,389	9,938
Major Customer Threshold, Percent of Operating Revenues	10.00%
Operating Segments [Member] | Natural Gas Distribution [Member]
Segment Reporting Information [Line Items]
NGD operating revenues	$ 1,117,498	970,124	797,800
Other regulated services	18,902	19,628	19,087
Operating revenues	1,136,400	989,752	816,887
Cost of gas	500,061	429,861	292,538
Environmental remediation	12,899	12,389	9,938
Revenue taxes	48,432	41,627	34,600
NGD margin	575,008	505,875	479,811
Operating Segments [Member] | Natural Gas Distribution [Member] | Northwest Natural Gas Company [Member]
Segment Reporting Information [Line Items]
Operating revenues	$ 1,136,400	$ 989,752	$ 816,887