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Fair Value Measurements (Details 4) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Fair Value Disclosures [Abstract]      
Sale Proceeds $ 1,637 $ 800 $ 1,230
Realized Gains 98 41 74
Realized Losses (31) (48) (58)
Interest and Dividend Income $ 38 $ 41 $ 39