Supplemental Cash Flow - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents	$ 17,907	$ 30,168	$ 471,079
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	25,512	35,454	475,864	$ 12,636
Northwest Natural Gas Company [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents	10,418	10,453	432,255
Restricted Cash	7,605	5,286	4,785
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	18,023	15,739	437,040	$ 8,907
Other Current Assets
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted Cash	$ 7,605	$ 5,286	$ 4,785