Long-Term Debt and Liquidity Matters - Estimated Fair Value of Long-Term Debt (Details) - USD ($) $ in Thousands |
Jun. 30, 2018 |
Dec. 31, 2017 |
---|---|---|
Estimated fair value of long-term debt, including current maturities | ||
Carrying Amount | $ 4,791,525 | $ 4,871,713 |
Fair Value | 4,953,048 | 5,304,956 |
Pinnacle West | ||
Estimated fair value of long-term debt, including current maturities | ||
Carrying Amount | 298,483 | 298,421 |
Fair Value | 292,767 | 298,608 |
APS | ||
Estimated fair value of long-term debt, including current maturities | ||
Carrying Amount | 4,493,042 | 4,573,292 |
Fair Value | $ 4,660,281 | $ 5,006,348 |