Summary of Significant Accounting Policies - Narrative (Details) $ / shares in Units, $ in Millions	1 Months Ended	12 Months Ended			36 Months Ended
	May. 31, 2014 $ / kWh	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2015 USD ($) $ / shares shares
Approximate remaining average useful lives of utility property
Cost of services, depreciation		$ 430	$ 396	$ 400
Depreciation rates (as a percent)		2.74%	2.77%	3.00%
Allowance for Funds Used During Construction
Composite rate used to calculate AFUDC (as a percent)		8.02%	8.47%	8.56%
Income Taxes
Percent likelihood largest tax benefit amount is realized (greater than)		50.00%
Intangible Assets
Amortization expense		$ 58	$ 53	$ 53
Estimated amortization expense on existing intangible assets over the next five years
2016		48			$ 48
2017		36			36
2018		18			18
2019		9			9
2020		$ 3			$ 3
Weighted average remaining amortization period for intangible assets		5 years
ARIZONA PUBLIC SERVICE COMPANY
Nuclear Fuel
Charges for the permanent disposal of spent nuclear fuel (in dollars per kWh) | $ / kWh	0.001
Preferred Stock
Preferred stock, shares authorized (in shares) | shares		15,535,000			15,535,000
Preferred stock par or stated value per share 1 (in dollars per share) | $ / shares		$ 25			$ 25
Preferred stock par or stated value per share 2 (in dollars per share) | $ / shares		50			50
Preferred stock par or stated value per share 3 (in dollars per share) | $ / shares		$ 100			$ 100
Pinnacle West
Preferred Stock
Preferred stock, shares authorized (in shares) | shares		10,000,000			10,000,000
Minimum
Approximate remaining average useful lives of utility property
Depreciation rates (as a percent)					0.30%
Maximum
Approximate remaining average useful lives of utility property
Depreciation rates (as a percent)					12.37%
Investments
Ownership percentage for classification as cost method investments by El Dorado		20.00%
Fossil plant
Approximate remaining average useful lives of utility property
Average useful life		19 years
Nuclear plant
Approximate remaining average useful lives of utility property
Average useful life		28 years
Other generation
Approximate remaining average useful lives of utility property
Average useful life		25 years
Transmission
Approximate remaining average useful lives of utility property
Average useful life		39 years
Distribution
Approximate remaining average useful lives of utility property
Average useful life		33 years
Other
Approximate remaining average useful lives of utility property
Average useful life		7 years