| Cover | Feb. 26, 2020 |
| Cover page. | |
| Document Type | 8-K |
| Document Period End Date | Feb. 26, 2020 |
| Entity Registrant Name | SOUTHWEST GAS HOLDINGS, INC. |
| Entity File Number | 001-37976 |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 81-3881866 |
| Entity Address, Address Line One | 5241 Spring Mountain Road |
| Entity Address, Address Line Two | Post Office Box 98510 |
| Entity Address, City or Town | Las Vegas |
| Entity Address, State or Province | NV |
| Entity Address, Postal Zip Code | 89193-8510 |
| City Area Code | 702 |
| Local Phone Number | 876‑7237 |
| Title of 12(b) Security | Southwest Gas Holdings, Inc. Common Stock, $1 Par Value |
| Trading Symbol | SWX |
| Security Exchange Name | NYSE |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001692115 |
| Amendment Flag | false |
