| Document and Entity Information | Dec. 31, 2021 |
| Document And Entity Information [Line Items] | |
| Amendment Flag | true |
| Entity Central Index Key | 0001692115 |
| Document Type | 8-K/A |
| Document Period End Date | Dec. 31, 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, State or Province | NV |
| 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 January 3, 2022 (the “Initial Form 8-K”), which described, among other matters, the closing of the transactions contemplated by that certain Purchase and Sale Agreement, dated as of October 5, 2021 by and between Dominion Energy Questar Corporation and the Company, pursuant to which the Company acquired all the equity interests in Dominion Energy Questar Pipeline, LLC (“DEQP”) and related entities (together with the transactions described above, the “Acquisition”). This Amendment No. 1 amends the Initial Form 8-K to include the financial statements referred to in Items 9.01(a) and 9.01(b) below relating to the Acquisition. |
| 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 |
