Gas Reserves (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Schedule of Investments [Line Items]
Gas Reserves, Current	$ 16,647,000	$ 15,704,000
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	6.00%	6.00%	8.00%
Gas Reserves, Current	$ 16,647,000	$ 15,704,000
Gas Reserves Noncurrent Gross	170,660,000	171,832,000
Gas Reserves Amortization	104,463,000	87,779,000
Total Gas Reserves	82,844,000	99,757,000
Deferred Taxes Related To Gas Reserves	20,071,000	22,712,000
Net Gas Reserves Investment	62,773,000	77,045,000
Investment in Additional Wells, Gas Reserves	$ 4,800,000	$ 5,800,000