v3.19.3.a.u2
Fair Value Measurement and Disclosure (Gains and Losses on Equity Securities) (Details) - Equity Securities [Member] - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]      
Total gains (losses) recognized on equity securities $ 301 $ (130) $ 326
Gains (Losses) recognized on equity securities sold 100 (10) 47
Unrealized gains (losses) recognized on equity securities held at end of period $ 201 $ (120) $ 279