Long-Term Debt and Liquidity Matters - Fair Value of Long-Term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Estimated fair value of long-term debt, including current maturities
Carrying Amount	$ 5,138,232	$ 4,871,713
Fair Value	5,233,563	5,304,956
Pinnacle West
Estimated fair value of long-term debt, including current maturities
Carrying Amount	448,796	298,421
Fair Value	443,955	298,608
ARIZONA PUBLIC SERVICE COMPANY
Estimated fair value of long-term debt, including current maturities
Carrying Amount	4,689,436	4,573,292
Fair Value	$ 4,789,608	$ 5,006,348