XML 37 R26.htm IDEA: XBRL DOCUMENT v3.10.0.1
Financial Derivative Instruments Narrative (Details) - USD ($)
$ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Derivative [Line Items]        
Derivative, Cost of Hedge $ 34 $ 34 $ 101 $ 102
Percentage of actual consumption hedged 80.00%   80.00%  
Current Unrealized Net Gains (Losses) in OCI $ 198   $ 198  
Maximum sum of derivatives of counterparty to be included in other (less than $20 million) $ 20   $ 20  
Maximum cash collateral provided as a percentage of derivative contract value (in hundredths) 100.00%   100.00%  
Maximum letter of credit percent of collateral 100.00%   100.00%  
Remainder of Current Year        
Derivative [Line Items]        
Derivative, Nonmonetary Notional Amount, Percent of Required Need, Coverage 79.00%   79.00%