Long-Term Debt and Liquidity Matters - Fair Value of Long-Term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Estimated fair value of long-term debt, including current maturities
Carrying Amount	$ 5,632,558	$ 5,138,232
Fair Value	6,194,392	5,233,563
Pinnacle West
Estimated fair value of long-term debt, including current maturities
Carrying Amount	449,425	448,796
Fair Value	450,822	443,955
ARIZONA PUBLIC SERVICE COMPANY
Estimated fair value of long-term debt, including current maturities
Carrying Amount	5,183,133	4,689,436
Fair Value	$ 5,743,570	$ 4,789,608