Regulatory Matters (Details) (APS, USD $)	0 Months Ended			1 Months Ended	0 Months Ended		12 Months Ended	0 Months Ended
	Jan. 01, 2014	Jan. 06, 2012	Jun. 01, 2011	Jan. 31, 2012	Apr. 01, 2014	Feb. 12, 2013	Dec. 31, 2014	Jan. 15, 2015	Feb. 01, 2015	Jun. 01, 2014	Apr. 15, 2014 MW	Dec. 31, 2013	Dec. 31, 2012	Jun. 01, 2012	Jul. 01, 2014	Jul. 12, 2013
Retired power plant costs
Regulatory Matters [Line Items]
Regulatory Asset, Net Book Value							$ 128,000,000
Lost Fixed Cost Recovery Mechanism
Change in regulatory asset
Rate Matter Cap Percentage of Retail Revenue							1.00%
ACC | Net Metering
Change in regulatory asset
Charge on future customers who install rooftop solar panels (in dollars per kWh)	0.70
Estimated monthly collection due to charge on future customers who install rooftop solar panels	4.90
Filing with the Arizona Corporation Commission | Arizona Renewable Energy Standard and Tariff 2014 [Member]
Change in regulatory asset
Rate Matter Additional Capacity from AZ Sun Projects											20
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)				0.03757
Approved base fuel rate (in dollars per 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 | 2013 DSMAC
Change in regulatory asset
Amount of proposed budget													87,600,000
Rate Matter, Approved Budget							68,900,000					68,900,000
Cost Recovery Mechanisms | Power Supply Adjustor (PSA)
Change in regulatory asset
Increase or decrease in PSA charge (in dollars per kWh)							0.004
Cost Recovery Mechanisms | Lost Fixed Cost Recovery Mechanism
Change in regulatory asset
Fixed costs recoverable per residential power lost (in dollars per kWh)							0.031
Fixed costs recoverable per non-residential power lost (in dollars per kWh)							0.023
Amount of adjustment approved representing prorated sales losses					25,300,000	5,100,000
Cost Recovery Mechanisms | Lost Fixed Cost Recovery Mechanism | Subsequent event
Change in regulatory asset
Amount of Adjustment Representing Prorated Sales Losses Pending Approval								38,500,000
Cost Recovery Mechanisms | ACC | RES
Change in regulatory asset
Plan term							5 years
Cost Recovery Mechanisms | ACC | 2013 DSMAC
Change in regulatory asset
Percentage of cumulative energy savings for current year														5.00%
Cost Recovery Mechanisms | ACC | RES implementation plan covering 2014-2018 timeframe
Change in regulatory asset
Amount of proposed budget															154,000,000	143,000,000
Rate Matter, Approved Budget							152,000,000
Cost Recovery Mechanisms | ACC | Power Supply Adjustor (PSA)
Change in regulatory asset
PSA rate for prior year (in dollars per kWh)							(0.001557)
Cost Recovery Mechanisms | ACC | Power Supply Adjustor (PSA) | Subsequent event
Change in regulatory asset
PSA rate (in dollars per kWh)									0.000887
Forward component of increase in PSA (in dollars per kWh)									0.001131
Historical component of increase in PSA (in dollars per kWh)									(0.000244)
Cost Recovery Mechanisms | FERC | Transmission Rates, Transmission Cost Adjustor and Other Transmission Matters
Change in regulatory asset
Increase in annual wholesale transmission rates										$ 5,900,000