Regulatory Matters (Details) $ in Millions	1 Months Ended
Jan. 31, 2018 USD ($)	Mar. 31, 2018 regulatory_commission
Public Utilities General Disclosures [Line Items]
Number of regulatory commissions \| regulatory_commission		2
Utah Commission
Public Utilities General Disclosures [Line Items]
Decreases in infrastructure rates due to impacts of 2017 Tax Reform Act \| $	$ 2.5

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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