Amount of direct costs of the business combination including legal, accounting, and other costs incurred to consummate the business acquisition.

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

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.

+ References

No definition available.

+ Details

Name:	us-gaap_BusinessAcquisitionLineItems
Namespace Prefix:	us-gaap_
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- Definition

This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 25
-Paragraph 23
-URI http://asc.fasb.org/extlink&oid=123586518&loc=d3e1043-128460

+ Details

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- Definition

The equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Details

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- Details

Name:	us-gaap_BusinessAcquisitionAxis=swx_DrumMember
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- Details

Name:	dei_LegalEntityAxis=swx_CertainMembersOfRiggsDistlerManagementMember
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Business Acquisitions - Narrative (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Nov. 30, 2021	Aug. 27, 2021
Questar Pipelines
Business Acquisition [Line Items]
Incurred and expensed acquisition costs	$ 18.5
Acquisition-related costs	0.0
Drum
Business Acquisition [Line Items]
Incurred and expensed acquisition costs			$ 14.0
Acquisition-related costs	$ 0.0
Certain Members Of Riggs Distler Management \| Drum
Business Acquisition [Line Items]
Ownership percentage by noncontrolling owners	1.42%	1.42%