Segment Information - Accounts Receivable for Services (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Centuri
Segment Reporting Information [Line Items]
Centuri accounts receivable for services provided to Southwest	$ 15,102	$ 15,235

The aggregate amount of receivables to be collected from related parties where one party can exercise control or significant influence over another party; including affiliates, owners or officers and their immediate families, pension trusts, and so forth, at the financial statement date. which are usually due within one year (or one business cycle).

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(k)(1))
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-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
-Paragraph 1
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-Publisher FASB
-Name Accounting Standards Codification
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Name:	us-gaap_DueFromRelatedPartiesCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant