Debt (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Short-term Debt, Other Disclosures [Abstract]
Short-term debt	$ 389,500,000	$ 304,525,000
Short-term Debt, Weighted Average Interest Rate, at Point in Time	1.10%	1.20%
Commercial Paper, Maximum Maturity	63 days
Commercial Paper, Average Maturity	34 days
Debt Instruments [Abstract]
Ratio of Indebtedness to Net Capital	0.605
Liabilities, Fair Value Disclosure [Abstract]
Long-term Debt	$ 1,044,932,000	$ 955,425,000
Unamortized Debt Issuance Expense	(8,309,000)	(7,480,000)
Debt Instrument, Fair Value Disclosure	1,174,500,000	1,136,311,000
Long-term Debt, Gross	1,053,241,000	962,905,000
Two-year Term Loan Due 2021
Liabilities, Fair Value Disclosure [Abstract]
Repayments of Debt	35,000,000
Northwest Natural Gas Company [Member]
Short-term Debt, Other Disclosures [Abstract]
Short-term debt	$ 245,500,000	$ 231,525,000
Short-term Debt, Weighted Average Interest Rate, at Point in Time	0.30%	0.40%
Maturities of Long-term Debt [Abstract]
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	$ 0
Long-term Debt, Maturities, Repayments of Principal in Year Two	90,000,000
Long-term Debt, Maturities, Repayments of Principal in Year Three	0
Long-term Debt, Maturities, Repayments of Principal in Year Four	30,000,000
Long-term Debt, Maturities, Repayments of Principal in Year Five	55,000,000
Long-term Debt, Maturities, Repayments of Principal after Year Five	819,700,000
Debt Instruments [Abstract]
Long-Term Debt, Current Maturities, Gross	0	$ 60,000,000
Long-term Debt, Excluding Current Maturities, Gross	994,700,000	864,700,000
Liabilities, Fair Value Disclosure [Abstract]
Long-term Debt	986,495,000	917,220,000
Unamortized Debt Issuance Expense	(8,205,000)	(7,480,000)
Debt Instrument, Fair Value Disclosure	1,110,741,000	1,097,348,000
Long-term Debt, Gross	994,700,000	924,700,000
Northwest Natural Gas Company [Member] | Note 3600 Series Due 2050
Debt Instruments [Abstract]
Secured Debt	$ 150,000,000	$ 150,000,000
Liabilities, Fair Value Disclosure [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	3.60%	3.60%
Northwest Natural Gas Company [Member] | Note 3869 Series Due 2049 [Member]
Debt Instruments [Abstract]
Secured Debt	$ 90,000,000	$ 90,000,000
Liabilities, Fair Value Disclosure [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	3.869%	3.869%
Northwest Natural Gas Company [Member] | Note 4110 Series Due 2048 [Member]
Debt Instruments [Abstract]
Secured Debt	$ 50,000,000	$ 50,000,000
Liabilities, Fair Value Disclosure [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	4.11%	4.11%
Northwest Natural Gas Company [Member] | Note 3685 Series Due 2047 [Member]
Debt Instruments [Abstract]
Secured Debt	$ 75,000,000	$ 75,000,000
Liabilities, Fair Value Disclosure [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	3.685%	3.685%
Northwest Natural Gas Company [Member] | Note 4136 Series Due 2046 [Member]
Debt Instruments [Abstract]
Secured Debt	$ 40,000,000	$ 40,000,000
Liabilities, Fair Value Disclosure [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	4.136%	4.136%
Northwest Natural Gas Company [Member] | Note 4000 Series Due 2042 [Member]
Debt Instruments [Abstract]
Secured Debt	$ 50,000,000	$ 50,000,000
Liabilities, Fair Value Disclosure [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	4.00%	4.00%
Northwest Natural Gas Company [Member] | Note 5250 Series Due 2035 [Member]
Debt Instruments [Abstract]
Secured Debt	$ 10,000,000	$ 10,000,000
Liabilities, Fair Value Disclosure [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	5.25%	5.25%
Northwest Natural Gas Company [Member] | Note 5660 Series Due 2033 [Member]
Debt Instruments [Abstract]
Secured Debt	$ 40,000,000	$ 40,000,000
Liabilities, Fair Value Disclosure [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	5.66%	5.66%
Northwest Natural Gas Company [Member] | Note 5820 Series Due 2032 [Member]
Debt Instruments [Abstract]
Secured Debt	$ 30,000,000	$ 30,000,000
Liabilities, Fair Value Disclosure [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	5.82%	5.82%
Northwest Natural Gas Company [Member] | Note 7850 Series Due 2030 [Member]
Debt Instruments [Abstract]
Secured Debt	$ 10,000,000	$ 10,000,000
Liabilities, Fair Value Disclosure [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	7.85%	7.85%
Northwest Natural Gas Company [Member] | Note 7740 Series Due 2030 [Member]
Debt Instruments [Abstract]
Secured Debt	$ 20,000,000	$ 20,000,000
Liabilities, Fair Value Disclosure [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	7.74%	7.74%
Northwest Natural Gas Company [Member] | Note 3141 Series Due 2029 [Member]
Debt Instruments [Abstract]
Secured Debt	$ 50,000,000	$ 50,000,000
Liabilities, Fair Value Disclosure [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	3.141%	3.141%
Northwest Natural Gas Company [Member] | Note 6650 Series Due 2028 [Member]
Debt Instruments [Abstract]
Secured Debt	$ 10,000,000	$ 10,000,000
Liabilities, Fair Value Disclosure [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	6.65%	6.65%
Northwest Natural Gas Company [Member] | Note 6650 Series Due 2027 [Member]
Debt Instruments [Abstract]
Secured Debt	$ 19,700,000	$ 19,700,000
Liabilities, Fair Value Disclosure [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	6.65%	6.65%
Northwest Natural Gas Company [Member] | Note 2822 Series Due 2027 [Member]
Debt Instruments [Abstract]
Secured Debt	$ 25,000,000	$ 25,000,000
Liabilities, Fair Value Disclosure [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	2.822%	2.822%
Northwest Natural Gas Company [Member] | Note 7000 Series Due 2027 [Member]
Debt Instruments [Abstract]
Secured Debt	$ 20,000,000	$ 20,000,000
Liabilities, Fair Value Disclosure [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	7.00%	7.00%
Northwest Natural Gas Company [Member] | Note 3211 Series Due 2026 [Member]
Debt Instruments [Abstract]
Secured Debt	$ 35,000,000	$ 35,000,000
Liabilities, Fair Value Disclosure [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	3.211%	3.211%
Northwest Natural Gas Company [Member] | Note 7050 Series Due 2026 [Member]
Debt Instruments [Abstract]
Secured Debt	$ 20,000,000	$ 20,000,000
Liabilities, Fair Value Disclosure [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	7.05%	7.05%
Northwest Natural Gas Company [Member] | Note 6520 Series Due 2025 [Member]
Debt Instruments [Abstract]
Secured Debt	$ 10,000,000	$ 10,000,000
Liabilities, Fair Value Disclosure [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	6.52%	6.52%
Northwest Natural Gas Company [Member] | Note 7720 Series Due 2025 [Member]
Debt Instruments [Abstract]
Secured Debt	$ 20,000,000	$ 20,000,000
Liabilities, Fair Value Disclosure [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	7.72%	7.72%
Northwest Natural Gas Company [Member] | Note 5620 Series Due 2023 [Member]
Debt Instruments [Abstract]
Secured Debt	$ 40,000,000	$ 40,000,000
Liabilities, Fair Value Disclosure [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	5.62%	5.62%
Northwest Natural Gas Company [Member] | Note 3542 Series Due 2023 [Member]
Debt Instruments [Abstract]
Secured Debt	$ 50,000,000	$ 50,000,000
Liabilities, Fair Value Disclosure [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	3.542%	3.542%
Northwest Natural Gas Company [Member] | Note 3176 Series Due 2021 [Member]
Debt Instruments [Abstract]
Secured Debt	$ 0	$ 50,000,000
Liabilities, Fair Value Disclosure [Abstract]
Debt Instrument, Interest Rate, Stated Percentage		3.176%
Northwest Natural Gas Company [Member] | Note 9050 Series Due 2021 [Member]
Debt Instruments [Abstract]
Secured Debt	0	$ 10,000,000
Liabilities, Fair Value Disclosure [Abstract]
Debt Instrument, Interest Rate, Stated Percentage		9.05%
Northwest Natural Gas Company [Member] | 364-Day Term Loan, Due 2022
Debt Outstanding
Proceeds from Issuance of Debt	100,000,000
Northwest Natural Gas Company [Member] | Note 3078 Series due 2051
Debt Instruments [Abstract]
Secured Debt	$ 130,000,000	$ 0
Liabilities, Fair Value Disclosure [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	3.078%	3.078%
Northwest Holdings Other [Member] | Corporate, Non-Segment [Member] | NWN Water Term Loan Due 2026
Credit Agreements [Abstract]
Debt Instrument Covenant Consolidated Indebtedness To Capitalization Ratio	70.00%
Liabilities, Fair Value Disclosure [Abstract]
Long-term Debt	$ 55,000,000
Debt Instrument, Interest Rate, Stated Percentage	0.90%
Line of Credit [Member]
Credit Agreements [Abstract]
Line of Credit Facility, Maximum Borrowing Capacity	$ 200,000,000
Line of Credit Facility, Amount Outstanding	144,000,000	$ 73,000,000
Line of Credit Facility Contingent Increase To Maximum Borrowing Capacity	$ 300,000,000
Debt Instrument Covenant Consolidated Indebtedness To Capitalization Ratio	70.00%
Line of Credit [Member] | Northwest Natural Gas Company [Member]
Credit Agreements [Abstract]
Line of Credit Facility, Maximum Borrowing Capacity	$ 400,000,000
Line of Credit Facility, Amount Outstanding	0	0
Line of Credit Facility Contingent Increase To Maximum Borrowing Capacity	$ 600,000,000
Debt Instrument Covenant Consolidated Indebtedness To Capitalization Ratio	70.00%
Letter of Credit [Member]
Credit Agreements [Abstract]
Line of Credit Facility, Maximum Borrowing Capacity	$ 40,000,000
Liabilities, Fair Value Disclosure [Abstract]
Letters of Credit Outstanding, Amount	0
Letter of Credit [Member] | Northwest Natural Gas Company [Member]
Credit Agreements [Abstract]
Line of Credit Facility, Maximum Borrowing Capacity	60,000,000
Liabilities, Fair Value Disclosure [Abstract]
Letters of Credit Outstanding, Amount	$ 0	$ 0