| Document and Entity Information | Aug. 27, 2021 |
| Document And Entity Information [Line Items] | |
| Entity Address, State or Province | NV |
| Amendment Flag | true |
| Entity Central Index Key | 0001692115 |
| Document Type | 8-K/A |
| Document Period End Date | Aug. 27, 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 | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Amendment Description | This Amendment No. 1 on Form 8-K/A amends the Current Report on Form 8-K of Southwest Gas Holdings, Inc., a Delaware corporation (the “Company”), filed with the Securities and Exchange Commission on August 30, 2021 (the “Initial Form 8-K”), which described, among other matters, the closing of the transactions contemplated by that certain Agreement and Plan of Merger, dated as of June 28, 2021 (the “Merger Agreement”) by and among Centuri Group, Inc. (“Centuri”), a wholly owned subsidiary of the Company, Electric T&D Holding LLC, a wholly owned subsidiary of Centuri, and ETDH Merger Sub, Inc. with Drum Parent, Inc. (“Drum”) and OCM Drum Investors, L.P., as representative of certain stockholders and option holders of Drum, pursuant to which Centuri acquired Riggs Distler & Company, Inc. This Amendment No. 1 amends the Initial Form 8-K to include the financial statements and unaudited pro forma financial information referred to in Item 9.01(a) and (b) below relating to the Merger. |
| 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 |
