| Document and Entity Information | Nov. 05, 2021 |
| Document And Entity Information [Line Items] | |
| Entity Address, State or Province | NV |
| Amendment Flag | false |
| Entity Central Index Key | 0001692115 |
| Document Type | 8-K |
| Document Period End Date | Nov. 5, 2021 |
| Entity Registrant Name | SOUTHWEST GAS HOLDINGS, INC. |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 001-37976 |
| Entity Tax Identification Number | 81-3881866 |
| Entity Address, Address Line One | 8360 S. Durango Dr. |
| Entity Address, Address Line Two | Post Office Box 98510 |
| Entity Address, City or Town | Las Vegas |
| Entity Address, Postal Zip Code | 89193-8510 |
| City Area Code | (702) |
| Local Phone Number | 876-7237 |
| Written Communications | false |
| Soliciting Material | true |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Common Stock [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | Southwest Gas Holdings, Inc. Common Stock, $1 par value |
| Trading Symbol | SWX |
| Security Exchange Name | NYSE |
| Preferred Stock [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | Preferred Stock Purchase Rights |
| Security Exchange Name | NYSE |
