Short-term and Long-term Investments, Restricted Deposits - Narrative (Details) $ in Millions	9 Months Ended
	Sep. 30, 2023 USD ($) position	Dec. 31, 2022 USD ($)
Schedule Of Investments And Restricted Deposits By Type [Line Items]
Accrued interest income | $	$ 144	$ 132
Positions from which gross unrealized losses were generated	6,355
Total investment positions	6,604
Commercial mortgage-backed securities
Schedule Of Investments And Restricted Deposits By Type [Line Items]
Investments recorded at fair value that carry rating of AAA Plus, weighted average (in years)	4 years
Rated Securities | External Credit Rating, Investment Grade | Investment Securities
Schedule Of Investments And Restricted Deposits By Type [Line Items]
Percentage of investments in rated securities carry an investment grade rating by nationally recognized statistical rating organizations	99.00%