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Quarterly Financial Data (Unaudited) Narrative (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Income Statement [Abstract]      
Impairment losses $ 74 $ 431 $ 1,039
Impairment of investments in unconsolidated affiliates $ 0 $ 0 $ 313