v3.19.3
Investments and Fair Value Measurement - Change In Equity Securities (Details) - USD ($)
$ in Millions
Sep. 30, 2019
Dec. 31, 2018
Fair Value Disclosures [Abstract]    
Initial cost basis $ 5,975 $ 6,001
Upward adjustments 1,984 1,984
Downward adjustments (including impairment) 0 0
Total carrying value at the end of the period $ 7,959 $ 7,985