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