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- Definition

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Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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- Definition

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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No definition available.

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Amount, after deduction of unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation.

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Debt - Narrative (Details) - USD ($)	1 Months Ended	6 Months Ended
Debt - Narrative (Details) - USD ($)	Jun. 30, 2025	Jun. 30, 2026	Jul. 31, 2026	Dec. 31, 2025
Debt Instrument [Line Items]
Weighted average interest rate		8.92%		9.23%
Commercial Paper Program \| Southwest Gas Corporation \| Commercial Paper
Debt Instrument [Line Items]
Commercial paper, maximum issuance capacity		$ 50,000,000
Commercial Paper Program \| Southwest Gas Corporation \| Commercial Paper \| Subsequent Event
Debt Instrument [Line Items]
Commercial paper, maximum issuance capacity			$ 100,000,000
8% Series, due August 2026 \| Debentures:
Debt Instrument [Line Items]
Debt instrument, stated interest rate		8.00%
Long-term debt, gross		$ 75,000,000.0
Medium-term notes, 7.92% series, due June 2027 \| Debentures:
Debt Instrument [Line Items]
Debt instrument, stated interest rate		7.92%
Long-term debt, gross		$ 25,000,000.0
Revolving Credit Facility \| Revolving Credit Agreement Due August 2029 \| Line of Credit
Debt Instrument [Line Items]
Credit facility maximum borrowing capacity		$ 300,000,000.0
Interest period		7 days
Long-term debt outstanding		$ 0
Revolving Credit Facility \| Revolving Credit Agreement Due August 2029 \| Line of Credit \| Minimum
Debt Instrument [Line Items]
Commitment fee, unfunded portion		0.075%
Revolving Credit Facility \| Revolving Credit Agreement Due August 2029 \| Line of Credit \| Maximum
Debt Instrument [Line Items]
Commitment fee, unfunded portion		0.20%
Revolving Credit Facility \| Revolving Credit Agreement Due August 2029 \| Line of Credit \| Secured Overnight Financing Rate (SOFR)
Debt Instrument [Line Items]
Debt, basis spread on interest variable rate		0.03839%
Revolving Credit Facility \| Revolving Credit Agreement Due August 2029 \| Southwest Gas Corporation
Debt Instrument [Line Items]
Credit facility maximum borrowing capacity		$ 400,000,000.0
Long-term debt outstanding		$ 0
Revolving Credit Facility \| Revolving Credit Agreement Due August 2029 \| Southwest Gas Corporation \| Secured Overnight Financing Rate (SOFR)
Debt Instrument [Line Items]
Debt, basis spread on variable rate		1.125%
Revolving Credit Facility \| Revolving Credit Agreement Due August 2029 \| Southwest Gas Corporation \| Base Rate
Debt Instrument [Line Items]
Debt, basis spread on variable rate		0.125%
Revolving Credit Facility \| Revolving Credit Agreement Due August 2029 \| Southwest Gas Corporation \| Line of Credit
Debt Instrument [Line Items]
Credit facility maximum borrowing capacity		$ 150,000,000.0
Interest period	7 days
Revolving Credit Facility \| Revolving Credit Agreement Due August 2029 \| Southwest Gas Corporation \| Line of Credit \| Minimum
Debt Instrument [Line Items]
Commitment fee, unfunded portion	0.075%
Revolving Credit Facility \| Revolving Credit Agreement Due August 2029 \| Southwest Gas Corporation \| Line of Credit \| Maximum
Debt Instrument [Line Items]
Commitment fee, unfunded portion	0.20%
Revolving Credit Facility \| Revolving Credit Agreement Due August 2029 \| Southwest Gas Corporation \| Line of Credit \| Secured Overnight Financing Rate (SOFR)
Debt Instrument [Line Items]
Debt, basis spread on interest variable rate	0.03839%
Revolving Credit Facility \| Revolving Credit Agreement Due August 2029 \| Southwest Gas Corporation \| Line of Credit \| Line of Credit
Debt Instrument [Line Items]
Credit facility maximum borrowing capacity		250,000,000.0
Bridge Loan \| Revolving Credit Agreement Due August 2029 \| Line of Credit
Debt Instrument [Line Items]
Credit facility maximum borrowing capacity		$ 30,000,000.0
Bridge Loan \| Revolving Credit Agreement Due August 2029 \| Southwest Gas Corporation \| Line of Credit
Debt Instrument [Line Items]
Credit facility maximum borrowing capacity	$ 30,000,000.0