v3.19.3.a.u2
Cash and Cash Equivalents and Marketable Securities - Narrative (Details) - USD ($)
$ in Millions
Dec. 31, 2019
Dec. 31, 2018
Cash and Cash Equivalents and Marketable Securities [Abstract]    
Gross unrealized gains on marketable securities $ 205 $ 24
Gross unrealized losses on marketable securities (24) (357)
Gross unrealized losses in continuous loss position for 12 months or longer $ (17) $ (332)