Derivative Accounting - Narrative (Details) $ in Millions	9 Months Ended
Sep. 30, 2018 USD ($)
Commodity Contracts
Derivative Accounting
Additional collateral to counterparties for energy related non-derivative instrument contracts	$ 94
Commodity Contracts \| Designated as Hedging Instruments
Derivative Accounting
Estimated loss before income taxes to be reclassified from accumulated other comprehensive income	$ 2
APS
Derivative Accounting
Percentage of unrealized gains and losses on certain derivatives deferred for future rate treatment	100.00%

The aggregate fair value of additional assets that would be required to be posted as collateral for non-derivative instruments with credit-risk related contingent features if the credit-risk-related contingent features were triggered at the end of the reporting period.

No definition available.

+ Details

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Namespace Prefix:	pnw_
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Balance Type:	debit
Period Type:	instant

- Definition

Percentage of unrealized gains and losses on certain derivatives deferred for future rate treatment pursuant to the PSA mechanism that would otherwise be recognized in income.

+ References

No definition available.

+ Details

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Namespace Prefix:	pnw_
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Period Type:	instant

- Definition

The estimated net amount of existing gains or losses on cash flow hedges at the reporting date expected to be reclassified to earnings within the next 12 months.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=112277219&loc=d3e80748-113994

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- 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

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- Details

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- Details

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- Details

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