Long-Term Debt and Liquidity Matters - Estimated Fair Value of Long-Term Debt (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Estimated fair value of long-term debt, including current maturities
Carrying Amount	$ 4,399,520	$ 4,146,785
Fair Value	4,770,844	4,425,789
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	4,274,520	4,021,785
Fair Value	$ 4,645,844	$ 4,300,789