v3.26.1
Previously Issued Condensed Consolidated Financial Statements - Schedule of Effects of the Prior-Period Errors on the Condensed Consolidated Statements of Income (Details) - USD ($)
$ / shares in Units, shares in Thousands, $ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Error Corrections and Prior Period Adjustments Restatement [Line Items]        
Utility infrastructure services revenues   $ 0   $ 0
Total operating revenues   396,318   1,142,734
Operations and maintenance $ 133,792 137,501 $ 266,793 268,168
Depreciation and amortization 77,846 68,940 177,449 162,630
Utility infrastructure services expenses   0   0
Total operating expenses 273,827 331,825 639,600 864,522
Operating income 84,327 64,493 303,673 278,212
Net interest deductions (44,052) (53,367) (89,795) (107,786)
Other income (deductions) 11,295 18,068 22,286 27,263
Total other (expenses) (32,757) (35,299) (67,509) (80,523)
Income (loss) from continuing operations before income taxes 51,570 29,194 236,164 197,689
Income tax expense (benefit) 9,448 29,925 55,668 64,132
Income (loss) from continuing operations 42,122 (731) 180,496 133,557
Loss from discontinued operations, net of income tax 0 (36,869) 0 (61,970)
Net income (loss) 42,122 (37,600) 180,496 71,587
Net income (loss) attributable to Southwest Gas Holdings, Inc. $ 42,122 $ (40,154) $ 180,496 $ 73,716
Earnings (loss) per share attributable to Southwest Gas Holdings, Inc.:        
Continuing operations (in USD per share) $ 0.58 $ (0.01) $ 2.49 $ 1.85
Discontinued operations (in USD per share) 0 (0.55) 0 (0.83)
Net earnings (loss) per share - basic (in USD per share) 0.58 (0.56) 2.49 1.02
Diluted earnings (loss) per share:        
Continuing operations (in USD per share) 0.58 (0.01) 2.49 1.85
Discontinued operations (in USD per share) 0 (0.55) 0 (0.83)
Net earnings (loss) per share - diluted (in USD per share) $ 0.58 $ (0.56) $ 2.49 $ 1.02
Weighted average shares:        
Basic (in shares) 72,516 72,088 72,479 72,050
Diluted (in shares) 72,665 72,088 72,617 72,195
Southwest Gas Corporation        
Error Corrections and Prior Period Adjustments Restatement [Line Items]        
Total operating revenues   $ 396,318   $ 1,144,834
Operations and maintenance $ 132,952 136,652 $ 264,455 266,059
Depreciation and amortization 77,685 68,940 177,288 162,630
Total operating expenses 272,826 330,976 637,101 862,413
Operating income 85,328 65,342 306,172 282,421
Net interest deductions (43,987) (44,737) (89,667) (89,368)
Other income (deductions) 8,420 17,806 14,135 27,108
Total other (expenses) (35,567) (26,931) (75,532) (62,260)
Income (loss) from continuing operations before income taxes 49,761 38,411 230,640 220,161
Income tax expense (benefit) 9,004 (7,235) 52,112 31,920
Net income (loss) 40,757 45,646 178,528 188,241
Net income (loss) attributable to Southwest Gas Holdings, Inc. $ 40,757 45,646 $ 178,528 188,241
As Reported        
Error Corrections and Prior Period Adjustments Restatement [Line Items]        
Utility infrastructure services revenues   724,052   1,274,133
Total operating revenues   1,120,370   2,416,867
Operations and maintenance   138,696   269,947
Depreciation and amortization   103,163   231,076
Utility infrastructure services expenses   657,671   1,186,242
Total operating expenses   1,024,914   2,120,989
Operating income   95,456   295,878
Net interest deductions   (71,612)   (143,893)
Other income (deductions)   18,421   27,136
Total other (expenses)   (53,191)   (116,757)
Income (loss) from continuing operations before income taxes   42,265   179,121
Income tax expense (benefit)   52,594   80,263
Income (loss) from continuing operations   (10,329)   98,858
Loss from discontinued operations, net of income tax   0   0
Net income (loss)   (10,329)   98,858
Net income (loss) attributable to Southwest Gas Holdings, Inc.   $ (12,883)   $ 100,987
Earnings (loss) per share attributable to Southwest Gas Holdings, Inc.:        
Continuing operations (in USD per share)   $ (0.18)   $ 1.40
Discontinued operations (in USD per share)   0   0
Net earnings (loss) per share - basic (in USD per share)   (0.18)   1.40
Diluted earnings (loss) per share:        
Continuing operations (in USD per share)   (0.18)   1.40
Discontinued operations (in USD per share)   0   0
Net earnings (loss) per share - diluted (in USD per share)   $ (0.18)   $ 1.40
Weighted average shares:        
Basic (in shares)   72,088   72,050
Diluted (in shares)   72,088   72,195
As Reported | Southwest Gas Corporation        
Error Corrections and Prior Period Adjustments Restatement [Line Items]        
Total operating revenues   $ 396,318   $ 1,142,734
Operating income   65,342   280,321
Income (loss) from continuing operations before income taxes   38,411   218,061
Income tax expense (benefit)   4,734   41,442
Net income (loss)   33,677   176,619
Net income (loss) attributable to Southwest Gas Holdings, Inc.   33,677   176,619
Adjustments        
Error Corrections and Prior Period Adjustments Restatement [Line Items]        
Utility infrastructure services revenues   0   0
Total operating revenues   0   0
Operations and maintenance   0   0
Depreciation and amortization   0   0
Utility infrastructure services expenses   0   0
Total operating expenses   0   0
Operating income   0   0
Net interest deductions   0   0
Other income (deductions)   0   0
Total other (expenses)   0   0
Income (loss) from continuing operations before income taxes   0   0
Income tax expense (benefit)   27,271   27,271
Income (loss) from continuing operations   (27,271)   (27,271)
Loss from discontinued operations, net of income tax   0   0
Net income (loss)   (27,271)   (27,271)
Net income (loss) attributable to Southwest Gas Holdings, Inc.   $ (27,271)   $ (27,271)
Earnings (loss) per share attributable to Southwest Gas Holdings, Inc.:        
Continuing operations (in USD per share)   $ (0.38)   $ (0.38)
Discontinued operations (in USD per share)   0   0
Net earnings (loss) per share - basic (in USD per share)   (0.38)   (0.38)
Diluted earnings (loss) per share:        
Continuing operations (in USD per share)   (0.38)   (0.38)
Discontinued operations (in USD per share)   0   0
Net earnings (loss) per share - diluted (in USD per share)   $ (0.38)   $ (0.38)
Weighted average shares:        
Basic (in shares)   72,088   72,050
Diluted (in shares)   72,088   72,195
Adjustments | Southwest Gas Corporation        
Error Corrections and Prior Period Adjustments Restatement [Line Items]        
Total operating revenues   $ 0   $ 2,100
Operating income   0   2,100
Income (loss) from continuing operations before income taxes   0   2,100
Income tax expense (benefit)   (11,969)   (9,522)
Net income (loss)   11,969   11,622
Net income (loss) attributable to Southwest Gas Holdings, Inc.   11,969   11,622
As Restated        
Error Corrections and Prior Period Adjustments Restatement [Line Items]        
Utility infrastructure services revenues   724,052   1,274,133
Total operating revenues   1,120,370   2,416,867
Operations and maintenance   138,696   269,947
Depreciation and amortization   103,163   231,076
Utility infrastructure services expenses   657,671   1,186,242
Total operating expenses   1,024,914   2,120,989
Operating income   95,456   295,878
Net interest deductions   (71,612)   (143,893)
Other income (deductions)   18,421   27,136
Total other (expenses)   (53,191)   (116,757)
Income (loss) from continuing operations before income taxes   42,265   179,121
Income tax expense (benefit)   79,865   107,534
Income (loss) from continuing operations   (37,600)   71,587
Loss from discontinued operations, net of income tax   0   0
Net income (loss)   (37,600)   71,587
Net income (loss) attributable to Southwest Gas Holdings, Inc.   $ (40,154)   $ 73,716
Earnings (loss) per share attributable to Southwest Gas Holdings, Inc.:        
Continuing operations (in USD per share)   $ (0.56)   $ 1.02
Discontinued operations (in USD per share)   0   0
Net earnings (loss) per share - basic (in USD per share)   (0.56)   1.02
Diluted earnings (loss) per share:        
Continuing operations (in USD per share)   (0.56)   1.02
Discontinued operations (in USD per share)   0   0
Net earnings (loss) per share - diluted (in USD per share)   $ (0.56)   $ 1.02
Weighted average shares:        
Basic (in shares)   72,088   72,050
Diluted (in shares)   72,088   72,195
Discontinued Operations        
Error Corrections and Prior Period Adjustments Restatement [Line Items]        
Utility infrastructure services revenues   $ (724,052)   $ (1,274,133)
Total operating revenues   (724,052)   (1,274,133)
Operations and maintenance   (1,195)   (1,779)
Depreciation and amortization   (34,223)   (68,446)
Utility infrastructure services expenses   (657,671)   (1,186,242)
Total operating expenses   (693,089)   (1,256,467)
Operating income   (30,963)   (17,666)
Net interest deductions   18,245   36,107
Other income (deductions)   (353)   127
Total other (expenses)   17,892   36,234
Income (loss) from continuing operations before income taxes   (13,071)   18,568
Income tax expense (benefit)   (49,940)   (43,402)
Income (loss) from continuing operations   36,869   61,970
Loss from discontinued operations, net of income tax   (36,869)   (61,970)
Net income (loss)   0   0
Net income (loss) attributable to Southwest Gas Holdings, Inc.   $ 0   $ 0
Earnings (loss) per share attributable to Southwest Gas Holdings, Inc.:        
Continuing operations (in USD per share)   $ 0.55   $ 0.83
Discontinued operations (in USD per share)   (0.55)   (0.83)
Net earnings (loss) per share - basic (in USD per share)   0   0
Diluted earnings (loss) per share:        
Continuing operations (in USD per share)   0.55   0.83
Discontinued operations (in USD per share)   (0.55)   (0.83)
Net earnings (loss) per share - diluted (in USD per share)   $ 0   $ 0
Weighted average shares:        
Basic (in shares)   72,088   72,050
Diluted (in shares)   72,088   72,195