Derivative Accounting (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Designated as Hedging Instruments
Derivative [Line Items]
Derivative liability	$ 0	$ 2,000
ARIZONA PUBLIC SERVICE COMPANY
Derivative [Line Items]
Percentage of unrealized gains and losses on certain derivatives deferred for future rate treatment before accounting treatment change	100.00%
Commodity Contracts
Derivative [Line Items]
Derivative liability	$ 96,422	$ 73,074
Additional collateral to counterparties for energy related non-derivative instrument contracts	110,000
Commodity Contracts | Designated as Hedging Instruments
Derivative [Line Items]
Estimated net gain (loss) before income taxes to be reclassified from accumulated other comprehensive income	$ (2,000)