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Fair Value Information (Narrative) (Details) - USD ($)
$ in Millions
Sep. 30, 2020
Dec. 31, 2019
Sep. 30, 2019
Fair Value, Inputs, Level 3      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis      
Redeemable Preferred Securities Of Subsidiaries Fair Value Disclosure   $ 29 $ 29
Fair Value, Measurements, Recurring | Net Asset Value or Its Equivalent      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis      
Cash Surrender Value, Fair Value Disclosure $ 71 76  
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis      
Derivatives Assets 70 34  
Derivatives Liability $ 32 $ 44