Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements - Summary of Fair Value and Carrying Value of Financial Assets and Liabilities (Footnotes) (Details)

v3.19.1
Fair Value Measurements - Summary of Fair Value and Carrying Value of Financial Assets and Liabilities (Footnotes) (Details) - USD ($)
$ in Millions
Mar. 31, 2019
Dec. 31, 2018
Fair Value Disclosures [Abstract]    
Amortized cost of investments $ 179 $ 173