XML 71 R58.htm IDEA: XBRL DOCUMENT v3.21.2
Derivative Accounting - Narrative (Details) - USD ($)
9 Months Ended
Jun. 30, 2021
Sep. 30, 2021
Derivative Accounting    
Amounts reclassified from accumulated other comprehensive income in next twelve months   $ 0
Commodity Contracts    
Derivative Accounting    
Aggregate fair value of derivative instruments in a net liability position   2,700,000
Additional collateral to counterparties for energy related non-derivative instrument contracts   87,000,000
Risk Management Assets | Credit Concentration Risk    
Derivative Accounting    
Aggregate fair value of derivative instruments in a net liability position   $ 195,000,000
Risk Management Assets | Credit Concentration Risk | Two Counterparties    
Derivative Accounting    
Concentration risk 28.00%  
APS    
Derivative Accounting    
Percentage of unrealized gains and losses on certain derivatives deferred for future rate treatment   100.00%