Gas Reserves (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Schedule of Investments [Line Items]
Gas Reserves, Current	$ 11,409,000	$ 15,278,000
Northwest Natural Gas Company [Member]
Schedule of Investments [Line Items]
Total Cumulative Gas Reserves Investment	188,000,000
Gas Reserves Investment	178,000,000
Cumulative Gross Investment	10,000,000
Additional Rate Per Therm	$ 0.4725
Gas Reserves Percent Gas Supplies YTD	5.00%	5.00%	6.00%
Gas Reserves, Current	$ 11,409,000	$ 15,278,000
Gas Reserves Noncurrent Gross	175,898,000	172,029,000
Gas Reserves Amortization	141,414,000	123,635,000
Total Gas Reserves	45,893,000	63,672,000
Deferred Taxes Related To Gas Reserves	10,572,000	15,515,000
Net Gas Reserves Investment	35,321,000	48,157,000
Investment in Additional Wells, Gas Reserves	$ 3,000,000.0	$ 3,800,000