Common Stock - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	Apr. 01, 2022	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Authorized (in shares)		100,000,000	100,000,000
Equity issuance	2,875,000
Issuance of common stock, net of issuance costs		$ 208,276	$ 17,501
Par Value (in dollars per share)		$ 0	$ 0
Shares issued (in shares)		35,525,000	31,129,000
ATM Equity Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Par Value (in dollars per share)		$ 0
Sale of Stock, Cumulative Commissions and Fees Paid		$ 1,400
Cumulative Proceeds Received on All Transactions		$ 69,700
Shares issued (in shares)		1,381,728
nwn:AttheMarketEquityProgramEquityAvailableforIssuance		$ 111,100
ATM Equity Program | Maximum [Member] | Scenario, Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cumulative Proceeds Received on All Transactions		$ 200,000
Stock Repurchase Plan [Member]
Stock Repurchase Program
Stock Repurchase Program, Number of Shares Authorized to be Repurchased		2,800,000
Stock Repurchase Program, Authorized Amount		$ 100,000
Treasury Stock, Shares, Acquired		0
Repurchases Since Plan Inception in Year 2000 [Member] | Stock Repurchase Plan [Member]
Stock Repurchase Program
Treasury Stock, Shares, Acquired		2,100,000
Treasury Stock, Value, Acquired, Cost Method		$ 83,300
Northwest Holdings [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Reserved Shares Dividend Reinvestment		394,102
Northwest Holdings [Member] | Employee Stock Purchase Plan Member [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance		319,777
Northwest Natural Gas Company [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Repayments of Short-term Debt	$ 130,000