Leases - Lease Expense - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Lessee, Lease, Description [Line Items]
Residual Value of Leased Asset	$ 4,500	$ 4,100	$ 4,500	$ 4,100	$ 4,300
Lease Expense [Abstract]
Operating Lease, Expense	1,728	954	3,424	2,208
Short-term Lease, Cost	$ 349	285	$ 569	483
Minimum [Member]
Operating Lease Terms [Abstract]
Lessee, Operating Lease, Term of Contract	2 months		2 months
Maximum [Member]
Operating Lease Terms [Abstract]
Lessee, Operating Lease, Term of Contract	19 years		19 years
Northwest Natural Gas Company [Member]
Lease Expense [Abstract]
Operating Lease, Expense	$ 1,710	914	$ 3,388	2,116
Short-term Lease, Cost	349	285	569	483
Other Northwest Holdings [Member] | Corporate, Non-Segment [Member]
Lease Expense [Abstract]
Operating Lease, Expense	$ 18	$ 40	$ 36	$ 92