Long-Term Debt and Liquidity Matters - Estimated Fair Value of Long-Term Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Estimated fair value of long-term debt, including current maturities
Carrying Amount	$ 4,162,236	$ 3,819,971
Fair Value	4,734,003	4,106,367
Pinnacle West
Estimated fair value of long-term debt, including current maturities
Carrying Amount	125,000	125,000
Fair Value	125,000	125,000
Arizona Public Service Company
Estimated fair value of long-term debt, including current maturities
Carrying Amount	4,037,236	3,694,971
Fair Value	$ 4,609,003	$ 3,981,367