Long-Term Debt and Liquidity Matters - Fair Value of Long-Term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Estimated fair value of long-term debt, including current maturities
Carrying Amount	$ 6,314,266	$ 5,632,558
Fair Value	7,612,841	6,194,392
Pinnacle West
Estimated fair value of long-term debt, including current maturities
Carrying Amount	496,321	449,425
Fair Value	509,050	450,822
ARIZONA PUBLIC SERVICE COMPANY
Estimated fair value of long-term debt, including current maturities
Carrying Amount	5,817,945	5,183,133
Fair Value	$ 7,103,791	$ 5,743,570