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Regulatory Matters - Settlement Agreement, Cost Recovery Mechanism and Net Metering (Details) |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1 Months Ended | 2 Months Ended | 3 Months Ended |  |  |  |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Mar. 27, 2017 USD ($) $ / kWh | Mar. 26, 2017 $ / kWh | Feb. 01, 2017 $ / kWh | Jan. 13, 2017 USD ($) | Dec. 20, 2016 | Jun. 01, 2016 USD ($) | Feb. 01, 2016 $ / kWh | Jan. 15, 2016 USD ($) | Jan. 01, 2016 USD ($) | Jun. 01, 2015 USD ($) | Mar. 02, 2015 USD ($) | Nov. 04, 2014 | Jan. 06, 2012 USD ($) $ / kWh | Jun. 01, 2011 USD ($) | Sep. 30, 2016 | Dec. 31, 2014 storage_system penetration_feeder MW | Apr. 30, 2014 workshop | Mar. 31, 2017 USD ($) $ / kWh | Mar. 31, 2016 USD ($) | Jan. 27, 2017 USD ($) | Dec. 05, 2016 USD ($) | Jul. 12, 2016 USD ($) | Jul. 01, 2016 USD ($) | Apr. 01, 2016 USD ($) | Jan. 12, 2016 USD ($) | Nov. 25, 2015 USD ($) | Mar. 20, 2015 project
Change in regulatory asset |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Deferred fuel and purchased power costs — current period |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 988,000 | $ (1,007,000) |  |  |  |  |  |  |  |
Amounts charged to customers |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 4,172,000 | (2,388,000) |  |  |  |  |  |  |  |
APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Change in regulatory asset |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Deferred fuel and purchased power costs — current period |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 988,000 | (1,007,000) |  |  |  |  |  |  |  |
Amounts charged to customers |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 4,172,000 | (2,388,000) |  |  |  |  |  |  |  |
RES 2014 | APS | Alternative to AZ Sun Program, Phase 1 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Request to build additional utility scale solar, capacity | MW |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 8 |  |  |  |  |  |  |  |  |  |  |
RES 2014 | APS | Alternative to AZ Sun Program Phase 2 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Request to build additional utility scale solar, capacity | MW |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2 |  |  |  |  |  |  |  |  |  |  |
Number of energy storage systems | storage_system |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2 |  |  |  |  |  |  |  |  |  |  |
Number of high solar penetration feeders | penetration_feeder |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2 |  |  |  |  |  |  |  |  |  |  |
Lost Fixed Cost Recovery Mechanisms | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Change in regulatory asset |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fixed costs recoverable per residential power lost (in dollars per kWh) | $ / kWh |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0.031 |  |  |  |  |  |  |  |  |
Fixed costs recoverable per non-residential power lost (in dollars per kWh) | $ / kWh |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0.023 |  |  |  |  |  |  |  |  |
Percentage of retail revenues |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1.00% |  |  |  |  |  |  |  |  |
Amount of adjustment representing prorated sales losses approval |  |  |  |  |  |  |  | $ 46,400,000 |  |  | $ 38,500,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Increase in amount of adjustment representing prorated sales losses |  |  |  |  |  |  |  | $ 7,900,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
ACC | Retail Rate Case Filing with Arizona Corporation Commission | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net retail base rate, increase | $ 94,600,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Non-fuel and non-depreciation base rate, increase | 87,200,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fuel-related base rate decrease | 53,600,000 |  |  |  |  |  |  |  |  |  |  |  | $ 153,100,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Base rate increase, changes in depreciation schedules | $ 61,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Authorized return on common equity (as a percent) | 10.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of debt in capital structure | 44.20% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of common equity in capital structure | 55.80% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate matter, environmental surcharge cap rate (in dollars per kWh) | $ / kWh | 0.00050 | 0.00016 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate matter, resource comparison proxy for exported energy (in dollars per kWh) | $ / kWh | 0.129 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net retail rate increase |  |  |  |  |  | $ 165,900,000 |  |  |  |  |  |  |  | $ 95,500,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Approximate percentage of increase in average retail customer bill |  |  |  |  |  |  |  |  |  |  |  |  |  | 6.60% |  |  |  |  |  |  |  |  |  |  |  |  |
Net change in base rates |  |  |  |  |  |  |  |  |  |  |  |  | 0 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Non-fuel base rate increase |  |  |  |  |  |  |  |  |  |  |  |  | $ 116,300,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Current base fuel rate (in dollars per kWh) | $ / kWh |  |  |  |  |  |  |  |  |  |  |  |  | 0.03757 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Approved base fuel rate (in dollars per kWh) | $ / kWh |  |  |  |  |  |  |  |  |  |  |  |  | 0.03207 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated amount of transfer of cost recovery for certain renewable energy projects from the RES surcharge to base rates |  |  |  |  |  |  |  |  |  |  |  |  | $ 36,800,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Change in regulatory asset |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Reduced system benefits charge, amount |  |  |  |  |  |  |  |  | $ 14,600,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
ACC | Retail Rate Case Filing with Arizona Corporation Commission | APS | AZ Sun Program Phase 2 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public utilities, minimum annual renewable energy standard and tariff | $ 10,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public utilities, maximum annual renewable energy standard and tariff | $ 15,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
ACC | RES | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Plan term |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 5 years |  |  |  |  |  |  |  |  |
ACC | RES 2016 | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount of approved budget |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 148,000,000 |  |
ACC | RES 2017 | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount of proposed budget |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 150,000,000 |  |  |  |
ACC | Modernization and Expansion of the Renewal Energy Standard | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Proposed renewal energy standard, percent of retail sales |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 30.00% |  |  |  |  |  |  |  |  |  |  |  |
Current renewal energy standard, percent of retail sales |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 15.00% |  |  |  |  |  |  |  |  |  |  |  |
ACC | DSMAC 2015 | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount of approved budget |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 68,900,000 |  | $ 68,900,000 |
Number of resource savings projects | project |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3
Additional budget approved |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 4,000,000 |  |  |  |  |
ACC | DSMC 2016 | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount of approved budget |  |  |  |  |  |  |  |  |  | $ 68,900,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
ACC | Electric energy efficiency standard | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of workshops | workshop |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3 |  |  |  |  |  |  |  |  |  |
Number of days to convene a workshop |  |  |  |  |  |  |  |  |  |  |  | 120 days |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
ACC | Power Supply Adjustor (PSA) | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Change in regulatory asset |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Beginning balance |  |  |  |  |  |  |  |  | $ (9,688,000) |  |  |  |  |  |  |  |  | $ 12,465,000 | (9,688,000) |  |  |  |  |  |  |  |
Deferred fuel and purchased power costs — current period |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 988,000 | (1,007,000) |  |  |  |  |  |  |  |
Amounts charged to customers |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 4,172,000 | (2,388,000) |  |  |  |  |  |  |  |
Ending balance |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 17,625,000 | $ (13,083,000) |  |  |  |  |  |  |  |
PSA rate (in dollars per kWh) | $ / kWh |  |  | (0.001348) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Forward component of increase in PSA (in dollars per kWh) | $ / kWh |  |  | (0.001027) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Historical component of increase in PSA (in dollars per kWh) | $ / kWh |  |  | (0.000321) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
ACC | Net Metering | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Change in regulatory asset |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost of service, resource comparison proxy method, maximum annual percentage decrease |  |  |  |  | 10.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost of service for interconnected DG system customers, grandfathered period |  |  |  |  | 20 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost of service for new customers, guaranteed export price period |  |  |  |  | 10 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
ACC | Residential Demand Response, Energy Storage and Load Management Program | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Additional budget approved |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 4,000,000 |  |  |  |  |  |
ACC | Demand Side Management Adjustor Charge 2017 | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount of proposed budget |  |  |  |  |  | 62,600,000 |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 66,600,000 |  |  |  |  |  |  |
United States Federal Energy Regulatory Commission | Open Access Transmission Tariff | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Change in regulatory asset |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Decrease in annual wholesale transmission rates |  |  |  |  |  |  |  |  |  | $ 17,600,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Increase in annual wholesale transmission rates |  |  |  |  |  | $ 24,900,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost Recovery Mechanisms | Lost Fixed Cost Recovery Mechanisms | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Change in regulatory asset |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Increase in amount of adjustment representing prorated sales losses |  |  |  | $ 17,300,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount of adjustment representing prorated sales losses pending approval |  |  |  | $ 63,700,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost Recovery Mechanisms | ACC | Power Supply Adjustor (PSA) | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Change in regulatory asset |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PSA rate for prior year (in dollars per kWh) | $ / kWh |  |  |  |  |  |  | 0.001678 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |

X
- Definition Amount of Adjustment Representing Prorated Sales Losses Approved + References No definition available. + Details
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Data Type: | xbrli:monetaryItemType
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X
- Definition Amount of Adjustment Representing Prorated Sales Losses Pending Approval + References No definition available. + Details
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Namespace Prefix: | pnw_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- References No definition available. + Details
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Balance Type: | na
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- Definition Deferred Fuel and Purchased Power Regulatory Asset (Liability), Current + References No definition available. + Details
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Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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X
- Definition Represents the forward component of increase in PSA. + References No definition available. + Details
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Namespace Prefix: | pnw_
Data Type: | us-types:perUnitItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the historical component of increase in PSA. + References No definition available. + Details
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Namespace Prefix: | pnw_
Data Type: | us-types:perUnitItemType
Balance Type: | na
Period Type: | duration

X
- Definition The amortization of deferred fuel and purchased power costs. + References No definition available. + Details
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Data Type: | xbrli:monetaryItemType
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- Definition Increase in Amount of Adjustment Representing Prorated Sales Losses + References No definition available. + Details
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Namespace Prefix: | pnw_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Represents the PSA rate (power supply adjustor) which provides for the adjustment of retail rates to reflect variations in retail fuel and purchased power costs. + References No definition available. + Details
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Namespace Prefix: | pnw_
Data Type: | us-types:perUnitItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the PSA rate prior for the prior years (power supply adjustor) which provides for the adjustment of retail rates to reflect variations in retail fuel and purchased power costs. + References No definition available. + Details
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Namespace Prefix: | pnw_
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- Definition Public Utilities, Cost Effective Energy Efficiency Programs, Number of Days to Convene a Workshop + References No definition available. + Details
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