Debt (Details)	3 Months Ended	9 Months Ended	12 Months Ended
	Mar. 31, 2024	Sep. 30, 2023	Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($) numberOfProjects	Dec. 31, 2022 USD ($)	Jan. 31, 2024 USD ($)	Aug. 04, 2023 USD ($)	Feb. 23, 2023 USD ($)
Maturities of Long-term Debt [Abstract]
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months				$ 150,868,000
Long-term Debt, Maturities, Repayments of Principal in Year Two				30,824,000
Long-term Debt, Maturities, Repayments of Principal in Year Three				110,852,000
Long-term Debt, Maturities, Repayments of Principal in Year Four				65,581,000
Long-term Debt, Maturities, Repayments of Principal in Year Five				10,866,000
Long-term Debt, Maturities, Repayments of Principal after Year Five				1,217,353,000
Debt Instruments [Abstract]
Long-Term Debt, Current Maturities, Gross				150,900,000	$ 90,700,000
Liabilities, Fair Value Disclosure [Abstract]
Long-term Debt				1,576,300,000	1,336,864,000
Other Long-Term Debt				6,600,000	6,200,000
Unamortized Debt Issuance Expense				10,044,000	8,987,000
Debt Instrument, Fair Value Disclosure				1,447,941,000	1,148,395,000
Long-term Debt, Gross				$ 1,586,344,000	1,345,851,000
Short-term Debt, Other Disclosures [Abstract]
Commercial Paper, Maximum Maturity				5 days
Commercial Paper, Average Maturity				4 days
Long-term debt				$ 1,425,435,000	1,246,167,000
Short-term debt				$ 89,780,000	258,200,000
Investments, Number of RNG Development Projects | numberOfProjects				4
NWN Water Term Loan Due 2026
Short-term Debt, Other Disclosures [Abstract]
Derivative, Fixed Interest Rate				3.80%
18 Month Credit Agreement Due March 15, 2024
Credit Agreements [Abstract]
Debt Instrument Covenant Consolidated Indebtedness To Capitalization Ratio		70.00%
Debt Outstanding
Proceeds from Issuance of Debt				$ 100,000,000.0	$ 100,000,000.0
Short-term Debt, Other Disclosures [Abstract]
Long-Term Debt, Weighted Average Interest Rate, at Point in Time				5.50%	4.20%
Derivative, Fixed Interest Rate				4.70%
18 Month Credit Agreement Due March 15, 2024 | Forecast [Member]
Short-term Debt, Other Disclosures [Abstract]
Short-Term Debt, Refinanced, Amount			$ 150,000,000
Note 5180 Series due 2034
Short-term Debt, Other Disclosures [Abstract]
Debt Instrument, Interest Rate, Stated Percentage							5.18%
Note 5230 Series due 2038
Short-term Debt, Other Disclosures [Abstract]
Debt Instrument, Interest Rate, Stated Percentage							5.23%
Line of Credit [Member]
Credit Agreements [Abstract]
Line of Credit Facility, Amount Outstanding				$ 73,000,000.0	$ 88,000,000.0
Short-term Debt, Other Disclosures [Abstract]
Short-term Debt, Weighted Average Interest Rate, at Point in Time				6.40%	5.30%
Short-term Debt, Weighted Average Interest Rate, at Point in Time				6.40%	5.30%
.0578 Series due 2028
Repayments of Long-term Debt [Abstract]
Debt Instrument, Redemption Price, Percentage of Principal Amount Redeemed				100.00%
Short-term Debt, Other Disclosures [Abstract]
Debt Instrument, Interest Rate, Stated Percentage				5.78%
Debt Instrument, Unused Borrowing Capacity, Amount				$ 100,000,000
.0578 Series due 2028 | Minimum [Member]
Short-term Debt, Other Disclosures [Abstract]
Debt Instrument, Redemption Price, Percentage				5.00%
0584 Series due 2028
Repayments of Long-term Debt [Abstract]
Debt Instrument, Redemption Price, Percentage of Principal Amount Redeemed				100.00%
Short-term Debt, Other Disclosures [Abstract]
Debt Instrument, Interest Rate, Stated Percentage				5.84%
Debt Instrument, Unused Borrowing Capacity, Amount				$ 50,000,000
0584 Series due 2028 | Minimum [Member]
Short-term Debt, Other Disclosures [Abstract]
Debt Instrument, Redemption Price, Percentage				5.00%
Northwest Natural Gas Company [Member]
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				30,000,000
Long-term Debt, Maturities, Repayments of Principal in Year Three				55,000,000
Long-term Debt, Maturities, Repayments of Principal in Year Four				64,700,000
Long-term Debt, Maturities, Repayments of Principal in Year Five				10,000,000
Long-term Debt, Maturities, Repayments of Principal after Year Five				1,215,000,000
Debt Instruments [Abstract]
Long-Term Debt, Current Maturities, Gross				0	$ 90,000,000
Long-term Debt, Excluding Current Maturities, Gross				1,374,700,000	1,044,700,000
Liabilities, Fair Value Disclosure [Abstract]
Long-term Debt				1,364,732,000	1,125,877,000
Unamortized Debt Issuance Expense				9,968,000	8,823,000
Debt Instrument, Fair Value Disclosure				1,236,559,000	944,383,000
Long-term Debt, Gross				$ 1,374,700,000	$ 1,134,700,000
Short-term Debt, Other Disclosures [Abstract]
Long-Term Debt, Weighted Average Interest Rate, at Point in Time				4.70%	4.50%
Long-term debt				$ 1,364,732,000	$ 1,035,935,000
Short-term debt				16,780,000	170,200,000
Northwest Natural Gas Company [Member] | Note 3600 Series Due 2050
Debt Instruments [Abstract]
Secured Debt				$ 150,000,000	$ 150,000,000
Short-term Debt, Other Disclosures [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
Short-term Debt, Other Disclosures [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
Short-term Debt, Other Disclosures [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
Short-term Debt, Other Disclosures [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
Short-term Debt, Other Disclosures [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
Short-term Debt, Other Disclosures [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
Short-term Debt, Other Disclosures [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
Short-term Debt, Other Disclosures [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
Short-term Debt, Other Disclosures [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
Short-term Debt, Other Disclosures [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
Short-term Debt, Other Disclosures [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
Short-term Debt, Other Disclosures [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
Short-term Debt, Other Disclosures [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
Short-term Debt, Other Disclosures [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
Short-term Debt, Other Disclosures [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
Short-term Debt, Other Disclosures [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
Short-term Debt, Other Disclosures [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
Short-term Debt, Other Disclosures [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
Short-term Debt, Other Disclosures [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
Short-term Debt, Other Disclosures [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				$ 0	$ 40,000,000
Short-term Debt, Other Disclosures [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				$ 0	$ 50,000,000
Short-term Debt, Other Disclosures [Abstract]
Debt Instrument, Interest Rate, Stated Percentage				3.542%	3.542%
Northwest Natural Gas Company [Member] | Note 4780 Series due 2052
Debt Instruments [Abstract]
Secured Debt				$ 140,000,000	$ 140,000,000
Short-term Debt, Other Disclosures [Abstract]
Debt Instrument, Interest Rate, Stated Percentage				4.78%	4.78%
Northwest Natural Gas Company [Member] | Note 3078 Series due 2051
Debt Instruments [Abstract]
Secured Debt				$ 130,000,000	$ 130,000,000
Short-term Debt, Other Disclosures [Abstract]
Debt Instrument, Interest Rate, Stated Percentage				3.078%	3.078%
Northwest Natural Gas Company [Member] | Note 5180 Series due 2034
Debt Instruments [Abstract]
Secured Debt				$ 80,000,000	$ 0
Short-term Debt, Other Disclosures [Abstract]
Debt Instrument, Interest Rate, Stated Percentage				5.18%	5.18%
Proceeds from Issuance of First Mortgage Bond				$ 80,000,000
Northwest Natural Gas Company [Member] | Note 5230 Series due 2038
Debt Instruments [Abstract]
Secured Debt				$ 50,000,000	$ 0		$ 50,000,000
Short-term Debt, Other Disclosures [Abstract]
Debt Instrument, Interest Rate, Stated Percentage				5.23%	5.23%
Northwest Natural Gas Company [Member] | Note 5750 Series due 2033
Debt Instruments [Abstract]
Secured Debt				$ 100,000,000	$ 0
Short-term Debt, Other Disclosures [Abstract]
Debt Instrument, Interest Rate, Stated Percentage				5.75%	5.75%
Proceeds from Issuance of Medium-term Notes				$ 100,000,000
Northwest Natural Gas Company [Member] | Note 5430 Series due 2053
Debt Instruments [Abstract]
Secured Debt				$ 100,000,000	$ 0
Short-term Debt, Other Disclosures [Abstract]
Debt Instrument, Interest Rate, Stated Percentage				5.43%	5.43%
Proceeds from Issuance of First Mortgage Bond				$ 100,000,000
Northwest Natural Gas Company [Member] | Commercial Paper
Short-term Debt, Other Disclosures [Abstract]
Short-term Debt, Weighted Average Interest Rate, at Point in Time				5.50%	4.60%
Short-term Debt, Weighted Average Interest Rate, at Point in Time				5.50%	4.60%
Short-term debt				$ 16,800,000	$ 170,200,000
NWN Water | NWN Water Term Loan Due 2026
Liabilities, Fair Value Disclosure [Abstract]
Long-term Debt				$ 55,000,000.0	$ 55,000,000.0
Short-term Debt, Other Disclosures [Abstract]
Long-Term Debt, Weighted Average Interest Rate, at Point in Time				4.70%	2.50%
NWN Water | 18 Month Credit Agreement Due March 15, 2024
Debt Outstanding
Proceeds from Issuance of Debt				$ 50,000,000.0	$ 50,000,000.0
Short-term Debt, Other Disclosures [Abstract]
Long-Term Debt, Weighted Average Interest Rate, at Point in Time				5.80%	4.20%
Northwest Holdings Other [Member]
Maturities of Long-term Debt [Abstract]
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months				$ 150,868,000
Long-term Debt, Maturities, Repayments of Principal in Year Two				824,000
Long-term Debt, Maturities, Repayments of Principal in Year Three				55,852,000
Long-term Debt, Maturities, Repayments of Principal in Year Four				881,000
Long-term Debt, Maturities, Repayments of Principal in Year Five				866,000
Long-term Debt, Maturities, Repayments of Principal after Year Five				2,353,000
Liabilities, Fair Value Disclosure [Abstract]
Long-term Debt, Gross				211,644,000
Northwest Holdings Other [Member] | Corporate, Non-Segment [Member] | NWN Water Term Loan Due 2026
Liabilities, Fair Value Disclosure [Abstract]
Long-term Debt				55,000,000.0
Line of Credit [Member]
Credit Agreements [Abstract]
Line of Credit Facility, Maximum Borrowing Capacity				200,000,000
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] | First Available Extension Period
Short-term Debt, Other Disclosures [Abstract]
Line of Credit Facility, Expiration Period				1 year
Line of Credit [Member] | Second Available Extension Period
Short-term Debt, Other Disclosures [Abstract]
Line of Credit Facility, Expiration Period				1 year
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 Contingent Increase To Maximum Borrowing Capacity				$ 600,000,000
Line of Credit [Member] | Northwest Natural Gas Company [Member] | First Available Extension Period
Short-term Debt, Other Disclosures [Abstract]
Line of Credit Facility, Expiration Period				1 year
Line of Credit [Member] | Northwest Natural Gas Company [Member] | Second Available Extension Period
Short-term Debt, Other Disclosures [Abstract]
Line of Credit Facility, Expiration Period				1 year
Letter of Credit [Member]
Credit Agreements [Abstract]
Line of Credit Facility, Maximum Borrowing Capacity				$ 40,000,000
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
Letters of Credit Outstanding, Amount				$ 1	$ 0			$ 15,000,000
Letter of Credit [Member] | Northwest Natural Gas Company [Member] | Subsequent Event [Member]
Credit Agreements [Abstract]
Line of Credit Facility, Maximum Borrowing Capacity						$ 100,000,000
Short-term Debt, Other Disclosures [Abstract]
Debt Instrument, Restrictive Covenants	70