CONDENSED CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Operating revenues:
Gas operating revenues	$ 502,827	$ 520,677	$ 1,351,089	$ 1,384,092
Utility infrastructure services revenues	333,493	312,862	1,771,609	1,575,130
Total operating revenues	836,320	833,539	3,122,698	2,959,222
Operating expenses:
Net cost of gas sold	160,821	192,604	353,381	426,260
Operations and maintenance	103,781	106,245	421,686	410,287
Depreciation and amortization	87,653	77,539	313,351	264,273
Taxes other than income taxes	16,378	16,206	62,500	60,847
Utility infrastructure services expenses	319,314	300,465	1,592,076	1,429,202
Total operating expenses	687,947	693,059	2,742,994	2,590,869
Operating income	148,373	140,480	379,704	368,353
Other income and (expenses):
Net interest deductions	(28,380)	(26,397)	(111,209)	(100,437)
Other income (deductions)	(20,770)	6,839	(17,524)	(6,253)
Total other income and (expenses)	(49,150)	(19,558)	(128,733)	(106,690)
Income before income taxes	99,223	120,922	250,971	261,663
Income tax expense	26,218	25,538	56,703	62,921
Net income	73,005	95,384	194,268	198,742
Net income attributable to noncontrolling interests	463	575	2,599	747
Net income attributable to Southwest Gas Holdings, Inc.	$ 72,542	$ 94,809	$ 191,669	$ 197,995
Earnings per share:
Basic (in USD per share)	$ 1.31	$ 1.78	$ 3.50	$ 3.91
Diluted (in USD per share)	$ 1.31	$ 1.77	$ 3.50	$ 3.91
Weighted average shares:
Basic (in shares)	55,310	53,369	54,726	50,640
Diluted (in shares)	55,363	53,424	54,792	50,701
Southwest Gas Corporation
Operating revenues:
Gas operating revenues	$ 502,827	$ 520,677	$ 1,351,089	$ 1,384,092
Operating expenses:
Net cost of gas sold	160,821	192,604	353,381	426,260
Operations and maintenance	103,088	105,542	419,720	408,165
Depreciation and amortization	64,725	57,612	222,733	199,467
Taxes other than income taxes	16,378	16,206	62,500	60,847
Total operating expenses	345,012	371,964	1,058,334	1,094,739
Operating income	157,815	148,713	292,755	289,353
Other income and (expenses):
Net interest deductions	(25,058)	(23,099)	(96,985)	(85,584)
Other income (deductions)	(20,536)	5,946	(16,965)	(6,691)
Total other income and (expenses)	(45,594)	(17,153)	(113,950)	(92,275)
Income before income taxes	112,221	131,560	178,805	197,078
Income tax expense	28,622	28,171	35,424	45,196
Net income	83,599	103,389	143,381	151,882
Net income attributable to Southwest Gas Holdings, Inc.	$ 83,599	$ 103,389	$ 143,381	$ 151,882