Debt - Schedule of Carrying Amounts and Estimated Fair Values of Long-Term Debt (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Debt Instrument [Line Items]
Less: current maturities	$ (42,770)	$ (42,552)
Long-term debt, less current maturities	4,648,958	4,609,838
Carrying Amount
Debt Instrument [Line Items]
Unamortized discount and debt issuance costs	(16,192)	(17,111)
Less: current maturities	(42,770)	(42,552)
Long-term debt, less current maturities	4,648,958	4,609,838
Southwest Gas Corporation
Debt Instrument [Line Items]
Long-term debt, less current maturities	3,502,411	3,501,543
Southwest Gas Corporation | Carrying Amount
Debt Instrument [Line Items]
Less: current maturities	0	0
Long-term debt, less current maturities	3,502,411	3,501,543
Centuri | Carrying Amount | Centuri secured revolving credit facility
Debt Instrument [Line Items]
Long-term debt, gross	125,229	77,121
Centuri | Fair Value | Centuri secured revolving credit facility
Debt Instrument [Line Items]
Long-term debt, gross	125,324	77,205
Debentures | Southwest Gas Corporation | Carrying Amount
Debt Instrument [Line Items]
Unamortized discount and debt issuance costs	(28,828)	(29,594)
Long-term debt	3,303,672	3,302,906
Revolving credit facility and commercial paper | Southwest Gas Corporation | Carrying Amount
Debt Instrument [Line Items]
Long-term debt	0	0
Revolving credit facility and commercial paper | Southwest Gas Corporation | Fair Value
Debt Instrument [Line Items]
Long-term debt	0	0
Industrial development revenue bonds | Southwest Gas Corporation | Carrying Amount
Debt Instrument [Line Items]
Unamortized discount and debt issuance costs	(1,261)	(1,363)
Long-term debt	198,739	198,637
Other debt obligations | Carrying Amount
Debt Instrument [Line Items]
Long-term debt, gross	88,905	96,599
Other debt obligations | Fair Value
Debt Instrument [Line Items]
Long-term debt, gross	$ 85,024	92,209
8% Series, due 2026 | Debentures | Southwest Gas Corporation
Debt Instrument [Line Items]
Debt instrument interest rate	8.00%
8% Series, due 2026 | Debentures | Southwest Gas Corporation | Carrying Amount
Debt Instrument [Line Items]
Long-term debt, gross	$ 75,000	75,000
8% Series, due 2026 | Debentures | Southwest Gas Corporation | Fair Value
Debt Instrument [Line Items]
Long-term debt, gross	$ 78,087	79,502
Medium-term notes, 7.92% series, due 2027 | Debentures | Southwest Gas Corporation
Debt Instrument [Line Items]
Debt instrument interest rate	7.92%
Medium-term notes, 7.92% series, due 2027 | Debentures | Southwest Gas Corporation | Carrying Amount
Debt Instrument [Line Items]
Long-term debt, gross	$ 25,000	25,000
Medium-term notes, 7.92% series, due 2027 | Debentures | Southwest Gas Corporation | Fair Value
Debt Instrument [Line Items]
Long-term debt, gross	$ 26,470	26,883
Medium-term notes, 6.76% series, due 2027 | Debentures | Southwest Gas Corporation
Debt Instrument [Line Items]
Debt instrument interest rate	6.76%
Medium-term notes, 6.76% series, due 2027 | Debentures | Southwest Gas Corporation | Carrying Amount
Debt Instrument [Line Items]
Long-term debt, gross	$ 7,500	7,500
Medium-term notes, 6.76% series, due 2027 | Debentures | Southwest Gas Corporation | Fair Value
Debt Instrument [Line Items]
Long-term debt, gross	$ 7,703	7,800
Notes, 5.8%, due 2027 | Debentures | Southwest Gas Corporation
Debt Instrument [Line Items]
Debt instrument interest rate	5.80%
Notes, 5.8%, due 2027 | Debentures | Southwest Gas Corporation | Carrying Amount
Debt Instrument [Line Items]
Long-term debt, gross	$ 300,000	300,000
Notes, 5.8%, due 2027 | Debentures | Southwest Gas Corporation | Fair Value
Debt Instrument [Line Items]
Long-term debt, gross	$ 306,630	309,180
Notes, 3.7%, due 2028 | Debentures | Southwest Gas Corporation
Debt Instrument [Line Items]
Debt instrument interest rate	3.70%
Notes, 3.7%, due 2028 | Debentures | Southwest Gas Corporation | Carrying Amount
Debt Instrument [Line Items]
Long-term debt, gross	$ 300,000	300,000
Notes, 3.7%, due 2028 | Debentures | Southwest Gas Corporation | Fair Value
Debt Instrument [Line Items]
Long-term debt, gross	$ 285,690	285,300
Notes, 5.45%, due 2028 | Debentures | Southwest Gas Corporation
Debt Instrument [Line Items]
Debt instrument interest rate	5.45%
Notes, 5.45%, due 2028 | Debentures | Southwest Gas Corporation | Carrying Amount
Debt Instrument [Line Items]
Long-term debt, gross	$ 300,000	300,000
Notes, 5.45%, due 2028 | Debentures | Southwest Gas Corporation | Fair Value
Debt Instrument [Line Items]
Long-term debt, gross	$ 304,920	307,170
Notes, 2.2%, due 2030 | Debentures | Southwest Gas Corporation
Debt Instrument [Line Items]
Debt instrument interest rate	2.20%
Notes, 2.2%, due 2030 | Debentures | Southwest Gas Corporation | Carrying Amount
Debt Instrument [Line Items]
Long-term debt, gross	$ 450,000	450,000
Notes, 2.2%, due 2030 | Debentures | Southwest Gas Corporation | Fair Value
Debt Instrument [Line Items]
Long-term debt, gross	$ 381,555	382,635
Notes, 4.05%, due 2032 | Debentures | Southwest Gas Corporation
Debt Instrument [Line Items]
Debt instrument interest rate	4.05%
Notes, 4.05%, due 2032 | Debentures | Southwest Gas Corporation | Carrying Amount
Debt Instrument [Line Items]
Long-term debt, gross	$ 600,000	600,000
Notes, 4.05%, due 2032 | Debentures | Southwest Gas Corporation | Fair Value
Debt Instrument [Line Items]
Long-term debt, gross	$ 549,840	563,940
Notes, 6.1%, due 2041 | Debentures | Southwest Gas Corporation
Debt Instrument [Line Items]
Debt instrument interest rate	6.10%
Notes, 6.1%, due 2041 | Debentures | Southwest Gas Corporation | Carrying Amount
Debt Instrument [Line Items]
Long-term debt, gross	$ 125,000	125,000
Notes, 6.1%, due 2041 | Debentures | Southwest Gas Corporation | Fair Value
Debt Instrument [Line Items]
Long-term debt, gross	$ 129,113	126,238
Notes, 4.875%, due 2043 | Debentures | Southwest Gas Corporation
Debt Instrument [Line Items]
Debt instrument interest rate	4.875%
Notes, 4.875%, due 2043 | Debentures | Southwest Gas Corporation | Carrying Amount
Debt Instrument [Line Items]
Long-term debt, gross	$ 250,000	250,000
Notes, 4.875%, due 2043 | Debentures | Southwest Gas Corporation | Fair Value
Debt Instrument [Line Items]
Long-term debt, gross	$ 215,200	214,050
Notes, 3.8%, due 2046 | Debentures | Southwest Gas Corporation
Debt Instrument [Line Items]
Debt instrument interest rate	3.80%
Notes, 3.8%, due 2046 | Debentures | Southwest Gas Corporation | Carrying Amount
Debt Instrument [Line Items]
Long-term debt, gross	$ 300,000	300,000
Notes, 3.8%, due 2046 | Debentures | Southwest Gas Corporation | Fair Value
Debt Instrument [Line Items]
Long-term debt, gross	$ 224,970	225,240
Notes, 4.15%, due 2049 | Debentures | Southwest Gas Corporation
Debt Instrument [Line Items]
Debt instrument interest rate	4.15%
Notes, 4.15%, due 2049 | Debentures | Southwest Gas Corporation | Carrying Amount
Debt Instrument [Line Items]
Long-term debt, gross	$ 300,000	300,000
Notes, 4.15%, due 2049 | Debentures | Southwest Gas Corporation | Fair Value
Debt Instrument [Line Items]
Long-term debt, gross	$ 232,860	236,370
Notes, 3.18%, due 2051 | Debentures | Southwest Gas Corporation
Debt Instrument [Line Items]
Debt instrument interest rate	3.18%
Notes, 3.18%, due 2051 | Debentures | Southwest Gas Corporation | Carrying Amount
Debt Instrument [Line Items]
Long-term debt, gross	$ 300,000	300,000
Notes, 3.18%, due 2051 | Debentures | Southwest Gas Corporation | Fair Value
Debt Instrument [Line Items]
Long-term debt, gross	196,110	197,760
Tax-exempt Series A, due 2028 | Industrial development revenue bonds | Southwest Gas Corporation | Carrying Amount
Debt Instrument [Line Items]
Long-term debt, gross	50,000	50,000
Tax-exempt Series A, due 2028 | Industrial development revenue bonds | Southwest Gas Corporation | Fair Value
Debt Instrument [Line Items]
Long-term debt, gross	50,000	50,000
2003 Series A, due 2038 | Industrial development revenue bonds | Southwest Gas Corporation | Carrying Amount
Debt Instrument [Line Items]
Long-term debt, gross	50,000	50,000
2003 Series A, due 2038 | Industrial development revenue bonds | Southwest Gas Corporation | Fair Value
Debt Instrument [Line Items]
Long-term debt, gross	50,000	50,000
2008 Series A, due 2038 | Industrial development revenue bonds | Southwest Gas Corporation | Carrying Amount
Debt Instrument [Line Items]
Long-term debt, gross	50,000	50,000
2008 Series A, due 2038 | Industrial development revenue bonds | Southwest Gas Corporation | Fair Value
Debt Instrument [Line Items]
Long-term debt, gross	50,000	50,000
2009 Series A, due 2039 | Industrial development revenue bonds | Southwest Gas Corporation | Carrying Amount
Debt Instrument [Line Items]
Long-term debt, gross	50,000	50,000
2009 Series A, due 2039 | Industrial development revenue bonds | Southwest Gas Corporation | Fair Value
Debt Instrument [Line Items]
Long-term debt, gross	50,000	50,000
Centuri secured term loan facility | Secured Debt | Centuri | Carrying Amount
Debt Instrument [Line Items]
Long-term debt, gross	991,375	994,238
Centuri secured term loan facility | Secured Debt | Centuri | Fair Value
Debt Instrument [Line Items]
Long-term debt, gross	$ 991,375	$ 996,723