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Regulatory Matters (Details) - APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1 Months Ended | 2 Months Ended | 12 Months Ended |  |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Feb. 01, 2017 $ / kWh | Jan. 13, 2017 USD ($) | Dec. 20, 2016 | Jul. 12, 2016 USD ($) | Jun. 01, 2016 USD ($) kWh $ / kWh | Feb. 01, 2016 $ / kWh | Jan. 15, 2016 USD ($) | Jan. 01, 2016 USD ($) | Dec. 31, 2015 USD ($) | Jun. 01, 2015 USD ($) | Mar. 02, 2015 USD ($) | Feb. 01, 2015 $ / kWh | Jan. 06, 2012 USD ($) $ / kWh | Jun. 01, 2011 USD ($) | Sep. 30, 2016 | Dec. 31, 2014 storage_system penetration_feeder MW | Apr. 30, 2014 workshop | Dec. 31, 2016 $ / kWh | Jan. 27, 2017 USD ($) | Dec. 05, 2016 USD ($) | Jul. 01, 2016 USD ($) | Apr. 01, 2016 USD ($) | Jul. 01, 2015 USD ($) | Mar. 20, 2015 USD ($) project
Lost Fixed Cost Recovery Mechanism |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate matter cap percentage of retail revenue |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1.00% |  |  |  |  |  |
ACC | 2016 DSMAC |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount of approved budget |  |  |  |  |  |  |  |  |  | $ 68,900,000 |  |  |  |  |  |  |  |  |  |  |  | $ 68,900,000 |  |
Additional approved budget |  |  |  | $ 4,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
ACC | 2017 DSMAC |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount of proposed budget |  |  |  |  | $ 62,600,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
ACC | Residential demand response, energy storage and load management program |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Additional approved budget |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 4,000,000 |  |  |  |
ACC | Electric Energy Efficiency Standard |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public utilities, cost effective energy efficiency programs, number of workshops | workshop |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3 |  |  |  |  |  |  |
Public utilities, cost effective efficiency programs, number of days to convene a workshop |  |  |  | 120 days |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
ACC | Modernization and Expansion of the Renewal Energy Standard |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Proposed renewal energy standard, percent of retail sales |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 30.00% |  |  |  |  |  |  |  |  |
Current renewal energy standard, percent of retail sales |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 15.00% |  |  |  |  |  |  |  |  |
ACC | Net Metering |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
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 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate matters, cost of service for new customers, guaranteed export price period |  |  | 10 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
ACC | Retail Rate Case Filing with Arizona Corporation Commission |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net retail rate increase |  |  |  |  | $ 165,900,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Adjuster account balance transferred into base rates |  |  |  |  |  |  |  |  | $ 267,600,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Approximate percentage of increase in average customer bill |  |  |  |  | 5.74% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Approximate percentage of increase in average residential customer bill |  |  |  |  | 7.96% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
original cost rate base |  |  |  |  | $ 6,800,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Required return on incremental fair value rate base above original cost rate base |  |  |  |  | 1.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Base rate for fuel and purchased power costs | $ / kWh |  |  |  |  | 0.029882 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Decrease in base rate for fuel and purchased power costs | $ / kWh |  |  |  |  | 0.03207 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Plan option, non-partial requirements customers, maximum average monthly energy usage | kWh |  |  |  |  | 600 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Case completion term |  |  |  |  | 12 months |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Reduced system benefits charge, amount |  |  |  |  |  |  |  | $ 14,600,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
FERC | Transmission rates, transmission cost adjustor and other transmission matters |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Increase (decrease) in annual wholesale transmission rates |  |  |  |  | $ 24,900,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Filing with the Arizona Corporation Commission | ACC | Retail rate case filing |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net retail rate increase |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 95,500,000 |  |  |  |  |  |  |  |  |  |
Approximate percentage of increase in the average retail customer bill |  |  |  |  |  |  |  |  |  |  |  |  |  | 6.60% |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net change in base rates |  |  |  |  |  |  |  |  |  |  |  |  | $ 0 |  |  |  |  |  |  |  |  |  |  |
Non-fuel base rate increase |  |  |  |  |  |  |  |  |  |  |  |  | 116,300,000 |  |  |  |  |  |  |  |  |  |  |
Fuel-related base rate decrease |  |  |  |  |  |  |  |  |  |  |  |  | $ 153,100,000 |  |  |  |  |  |  |  |  |  |  |
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 |  |  |  |  |  |  |  |  |  |  |
Authorized return on common equity (as a percent) |  |  |  |  |  |  |  |  |  |  |  |  | 10.00% |  |  |  |  |  |  |  |  |  |  |
Percentage of debt in capital structure |  |  |  |  |  |  |  |  |  |  |  |  | 46.10% |  |  |  |  |  |  |  |  |  |  |
Percentage of common equity in capital structure |  |  |  |  |  |  |  |  |  |  |  |  | 53.90% |  |  |  |  |  |  |  |  |  |  |
Deferral of property taxes in 2012, if Arizona property tax rates increase (as a percent) |  |  |  |  |  |  |  |  |  |  |  |  | 25.00% |  |  |  |  |  |  |  |  |  |  |
Deferral of property taxes in 2013, if Arizona property tax rates increase (as a percent) |  |  |  |  |  |  |  |  |  |  |  |  | 50.00% |  |  |  |  |  |  |  |  |  |  |
Deferral of property taxes for 2014 and subsequent years, if Arizona property tax rates increase (as a percent) |  |  |  |  |  |  |  |  |  |  |  |  | 75.00% |  |  |  |  |  |  |  |  |  |  |
Deferral of property taxes in all years, if Arizona property tax rates decrease (as a percent) |  |  |  |  |  |  |  |  |  |  |  |  | 100.00% |  |  |  |  |  |  |  |  |  |  |
Elimination of the sharing provision of fuel and purchased power costs |  |  |  |  |  |  |  |  |  |  |  |  | 9 |  |  |  |  |  |  |  |  |  |  |
Period to process the subsequent rate cases |  |  |  |  |  |  |  |  |  |  |  |  | 12 months |  |  |  |  |  |  |  |  |  |  |
ACC staff sufficiency findings, general period of time |  |  |  |  |  |  |  |  |  |  |  |  | 30 days |  |  |  |  |  |  |  |  |  |  |
Filing with the Arizona Corporation Commission | ACC | Retail rate case filing | Maximum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Annual cost recovery due to modifications to the Environmental Improvement Surcharge |  |  |  |  |  |  |  |  |  |  |  |  | $ 5,000,000 |  |  |  |  |  |  |  |  |  |  |
Cost Recovery Mechanisms | Lost Fixed Cost Recovery Mechanism |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
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 |  |  |  |  |  |
Amount of adjustment approved representing prorated sales losses |  |  |  |  |  |  |  |  |  |  | $ 38,500,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Amount of adjustment representing prorated sales losses pending approval |  |  |  |  |  |  | $ 46,400,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Increase in amount of adjustment representing prorated sales losses |  |  |  |  |  |  | $ 7,900,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost Recovery Mechanisms | ACC | 2015 DSMAC |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount of proposed budget |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 68,900,000
Rate matter number of resource savings projects | project |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3
Cost Recovery Mechanisms | ACC | RES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Plan term |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 5 years |  |  |  |  |  |
Cost Recovery Mechanisms | ACC | Arizona Renewable Energy Standard and Tariff 2016 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount of proposed budget |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 148,000,000 |
Cost Recovery Mechanisms | ACC | Arizona Renewable Energy Standard and Tariff 2017 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount of proposed budget |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 150,000,000 |  |  |
Cost Recovery Mechanisms | ACC | Power Supply Adjustor (PSA) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Maximum increase (decrease) in PSA rate (in dollars per kWh) | $ / kWh |  |  |  |  |  |  |  |  |  |  |  | 0.004 |  |  |  |  |  |  |  |  |  |  |  |
PSA rate (in dollars per kWh) | $ / kWh |  |  |  |  |  | 0.001678 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost Recovery Mechanisms | FERC | Transmission rates, transmission cost adjustor and other transmission matters |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Increase (decrease) in annual wholesale transmission rates |  |  |  |  |  |  |  |  |  | $ (17,600,000) |  |  |  |  |  |  |  |  |  |  |  |  |  |
Subsequent Event | ACC | 2017 DSMAC |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount of proposed budget |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 66,600,000 |  |  |  |  |
Subsequent Event | ACC | Power Supply Adjustor (PSA) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PSA rate (in dollars per kWh) | $ / kWh | (0.001348) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Forward component of PSA rate (in dollars per kWh) | $ / kWh | (0.001027) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Historical component of PSA rate (in dollars per kWh) | $ / kWh | (0.000321) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Subsequent Event | ACC | Retail Rate Case Filing with Arizona Corporation Commission |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Case completion extension term |  | 33 days |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Subsequent Event | Cost Recovery Mechanisms | Lost Fixed Cost Recovery Mechanism |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount of adjustment representing prorated sales losses pending approval |  | $ 63,700,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Increase in amount of adjustment representing prorated sales losses |  | $ 17,300,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Four Corners Power Plant | ACC | Retail Rate Case Filing with Arizona Corporation Commission |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Authorization to defer for potential future recovery of construction costs |  |  |  |  | 400,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ocotillo Plant | ACC | Retail Rate Case Filing with Arizona Corporation Commission |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Authorization to defer for potential future recovery of construction costs |  |  |  |  | $ 500,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Alternative to AZ Sun Program, Phase 1 | Arizona Renewable Energy Standard and Tariff 2014 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate matter additional capacity from AZ Sun projects | MW |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 8 |  |  |  |  |  |  |  |
Alternative to AZ Sun Program Phase 2 | Arizona Renewable Energy Standard and Tariff 2014 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate matter additional capacity from AZ Sun projects | MW |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2 |  |  |  |  |  |  |  |
Number of energy storage systems | storage_system |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2 |  |  |  |  |  |  |  |
Number of high solar penetration feeders | penetration_feeder |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2 |  |  |  |  |  |  |  |

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

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

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

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