| Document and Entity Information Document | Aug. 07, 2020 |
| Document Information [Line Items] | |
| Entity Emerging Growth Company | false |
| Title of 12(b) Security | Common Stock |
| City Area Code | (503) |
| Entity Address, Address Line One | 250 SW Taylor Street |
| Entity Registrant Name | NORTHWEST NATURAL HOLDING COMPANY |
| Document Type | 8-K |
| Document Period End Date | Aug. 7, 2020 |
| Entity Central Index Key | 0001733998 |
| Amendment Flag | false |
| Entity File Number | 1-38681 |
| Entity Incorporation, State or Country Code | OR |
| Entity Tax Identification Number | 82-4710680 |
| Entity Address, City or Town | Portland |
| Entity Address, State or Province | OR |
| Entity Address, Postal Zip Code | 97204 |
| Local Phone Number | 226-4211 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Trading Symbol | NWN |
| Security Exchange Name | NYSE |
| Northwest Natural Gas Company [Member] | |
| Document Information [Line Items] | |
| Entity Emerging Growth Company | false |
| City Area Code | (503) |
| Entity Address, Address Line One | 250 SW Taylor Street |
| Entity Registrant Name | NORTHWEST NATURAL GAS COMPANY |
| Document Type | 8-K |
| Document Period End Date | Aug. 7, 2020 |
| Entity Central Index Key | 0000073020 |
| Amendment Flag | false |
| Entity File Number | 1-15973 |
| Entity Incorporation, State or Country Code | OR |
| Entity Tax Identification Number | 93-0256722 |
| Entity Address, City or Town | Portland |
| Entity Address, State or Province | OR |
| Entity Address, Postal Zip Code | 97204 |
| Local Phone Number | 226-4211 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
