Unrealized and Realized Gain/Loss (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Financial [Member]
Derivative [Line Items]
Derivative, Gain on Derivative		$ 11,300
Derivative, Loss on Derivative	$ (2,100)
Northwest Holdings and Northwest Natural [Member] | Natural gas commodity
Derivative [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	371	(345)
Northwest Holdings and Northwest Natural [Member] | Foreign exchange
Derivative [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	0	0
Northwest Holdings and Northwest Natural [Member] | Benefit (expense) to cost of gas | Natural gas commodity
Derivative [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	5,343	7,007
Northwest Holdings and Northwest Natural [Member] | Benefit (expense) to cost of gas | Foreign exchange
Derivative [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	466	89
Northwest Holdings and Northwest Natural [Member] | Sales [Member] | Natural gas commodity
Derivative [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	2,433	(2,367)
Northwest Holdings and Northwest Natural [Member] | Sales [Member] | Foreign exchange
Derivative [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	0	0
Deferred Derivative Gain (Loss) [Member] | Northwest Holdings and Northwest Natural [Member] | Natural gas commodity
Derivative [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	(7,405)	9,029
Deferred Derivative Gain (Loss) [Member] | Northwest Holdings and Northwest Natural [Member] | Foreign exchange
Derivative [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	$ (466)	$ (89)