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Fair Value Information (Narrative) (Details) - USD ($)
$ in Millions
Mar. 31, 2021
Dec. 31, 2020
Mar. 31, 2020
Fair Value, Inputs, Level 3      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis      
Redeemable Preferred Securities Of Subsidiaries Fair Value Disclosure   $ 28 $ 28
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 $ 73    
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis      
Derivatives Assets 41 44  
Derivatives Liability $ 62 $ 92