Regulatory Matters (Details)												2 Months Ended	3 Months Ended	9 Months Ended
	Jun. 01, 2015 USD ($)	Apr. 02, 2015 USD ($) $ / kWh	Mar. 02, 2015 USD ($)	Feb. 01, 2015 $ / kWh	Jun. 01, 2014 USD ($)	Apr. 15, 2014 Customer MW	Mar. 01, 2014 USD ($)	Feb. 01, 2014 $ / kWh	Jan. 01, 2014 USD ($) $ / kWh	Jan. 06, 2012 USD ($) $ / kWh	Jun. 01, 2011 USD ($)	Apr. 30, 2014 workshop	Jan. 31, 2016 $ / kWh	Sep. 30, 2015 USD ($) $ / kWh	Sep. 30, 2014 USD ($)	Jul. 01, 2015 USD ($)	Mar. 20, 2015 USD ($) project	Dec. 31, 2014 USD ($)	Dec. 19, 2014 MW	Jul. 01, 2014 USD ($)	Mar. 11, 2014 USD ($)	Jul. 12, 2013 USD ($)	Dec. 31, 2012 USD ($)	Jun. 01, 2012
Change in regulatory asset
Deferred fuel and purchased power costs — current period														$ 137,000	$ 26,880,000
Amounts charged to customers														(19,284,000)	(31,724,000)
APS
Change in regulatory asset
Deferred fuel and purchased power costs — current period														137,000	26,880,000
Amounts charged to customers														$ (19,284,000)	(31,724,000)
APS | Filing with the Arizona Corporation Commission | ACC | Retail rate case filing
Public Utilities, General Disclosures [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
APS | 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
APS | RES | Cost Recovery Mechanisms | ACC
Settlement Agreement
Plan term														5 years
APS | 2014 RES | Cost Recovery Mechanisms | ACC
Settlement Agreement
Amount of proposed budget																						$ 143,000,000
APS | 2014 RES | AZ Sun Program | Filing with the Arizona Corporation Commission
Settlement Agreement
Request to build additional utility scale solar, capacity | MW						20
APS | 2014 RES | Alternative to AZ Sun Program | Filing with the Arizona Corporation Commission
Settlement Agreement
Request to build additional utility scale solar, capacity | MW						10
Additional capacity from APS-owned non AZ Sun projects, impacted customers | Customer						1,500
APS | 2014 RES | Alternative to AZ Sun Program, Phase 1 | Filing with the Arizona Corporation Commission
Settlement Agreement
Request to build additional utility scale solar, capacity | MW																			8
APS | 2014 RES | Alternative to AZ Sun Program Phase 2 | Filing with the Arizona Corporation Commission
Settlement Agreement
Request to build additional utility scale solar, capacity | MW																			2
APS | 2015 RES | Cost Recovery Mechanisms | ACC
Settlement Agreement
Amount of proposed budget																				$ 154,000,000
Amount of approved budget																		$ 152,000,000
APS | 2016 RES | Cost Recovery Mechanisms | ACC
Settlement Agreement
Amount of proposed budget																$ 148,000,000
APS | 2013 DSMAC | Cost Recovery Mechanisms
Settlement Agreement
Amount of approved budget																					$ 68,900,000
APS | 2013 DSMAC | Cost Recovery Mechanisms | ACC
Settlement Agreement
Amount of proposed budget																							$ 87,600,000
Percentage of cumulative energy savings for current year																								5.00%
APS | 2014 DSMAC | Cost Recovery Mechanisms | ACC
Settlement Agreement
Amount of approved budget																					$ 68,900,000
APS | 2015 DSMAC | Cost Recovery Mechanisms | ACC
Settlement Agreement
Amount of proposed budget																	$ 68,900,000
Number of resource savings projects | project																	3
APS | 2016 DSMAC | Cost Recovery Mechanisms | ACC
Settlement Agreement
Amount of proposed budget	$ 68,900,000
Proposed rate reduction percentage	12.00%
APS | Electric energy efficiency standard | ACC
Settlement Agreement
Number of workshops | workshop												3
APS | Power Supply Adjustor (PSA) | Cost Recovery Mechanisms | ACC
Change in regulatory asset
Beginning balance									$ 21,000,000					$ 7,000,000	21,000,000
Deferred fuel and purchased power costs — current period														0	27,000,000
Amounts charged to customers														(19,000,000)	(32,000,000)
Ending balance														$ (12,000,000)	$ 16,000,000
PSA rate (in dollars per kWh) | $ / kWh				0.000887
PSA rate for prior year (in dollars per kWh) | $ / kWh								0.001557
Forward component of increase in PSA (in dollars per kWh) | $ / kWh				0.001131
Historical component of increase in PSA (in dollars per kWh) | $ / kWh				(0.000244)
APS | Power Supply Adjustor (PSA) | Cost Recovery Mechanisms | ACC | Forecast
Change in regulatory asset
Transition component increase in PSA (in dollars per kWh) | $ / kWh													(0.004936)
APS | Transmission Rates, Transmission Cost Adjustor and Other Transmission Matters | Cost Recovery Mechanisms | FERC
Change in regulatory asset
Increase in annual wholesale transmission rates	$ 17,600,000				$ 5,900,000
APS | Lost Fixed Cost Recovery Mechanism
Change in regulatory asset
Percentage of retail revenues														1.00%
APS | Lost Fixed Cost Recovery Mechanism | Cost Recovery Mechanisms
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
Amount of adjustment approved representing prorated sales losses			$ 38,500,000				$ 25,300,000
APS | Net Metering | ACC
Change in regulatory asset
Charge on future customers who install rooftop solar panels (in dollars per kWh) | $ / kWh									0.70					0.70
Estimated monthly collection due to charge on future customers who install rooftop solar panels									$ 4.90
Proposed fixed grid access charge on new residential solar customers (in dollars per KWh) | $ / kWh		3.00
Estimated monthly collection due to charge on new residential solar customers		$ 21