XML 66 R53.htm IDEA: XBRL DOCUMENT v3.19.1
Derivative Instruments and Hedging Activities - Effects of Derivatives on Statements of Income and AOCI (Details) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Mar. 31, 2019
Mar. 31, 2018
Derivatives Not Subject to PGC and DS Mechanisms: | Operating and administrative expenses        
Derivative Instruments, Gain (Loss)        
Location of (Loss) Gain Recognized in Income $ 129 $ 12    
Not designated as hedging instruments | Commodity contracts | Operating and administrative expenses        
Derivative Instruments, Gain (Loss)        
Location of (Loss) Gain Recognized in Income     $ (267) $ 161
Cash Flow Hedges | Interest rate contracts        
Derivative Instruments, Gain (Loss)        
Loss Recognized in AOCI (873) 0 (2,558) 0
Cash Flow Hedges | Interest rate contracts | Interest expense        
Derivative Instruments, Gain (Loss)        
Location of Loss Reclassified from AOCI into Income $ (870) $ (872) $ (1,742) $ (1,743)