Short-term and Long-term Investments, Restricted Deposits - Contractual Maturities of Short-Term and Long-Term Investments and Restricted Deposits (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Investments
Amortized Cost
One year or less	$ 2,121	$ 2,207
One year through five years	7,421	7,651
Five years through ten years	3,931	4,066
Greater than ten years	123	135
Asset-backed securities	4,208	3,522
Amortized Cost	17,804	17,581
Fair Value
One year or less	2,091	2,179
One year through five years	6,906	7,147
Five years through ten years	3,501	3,613
Greater than ten years	113	129
Asset-backed securities	3,874	3,234
Fair Value	16,485	16,302
Restricted Deposits
Amortized Cost
One year or less	537	534
One year through five years	531	524
Five years through ten years	312	224
Greater than ten years	32	0
Asset-backed securities	0	0
Amortized Cost	1,412	1,282
Fair Value
One year or less	534	532
One year through five years	496	490
Five years through ten years	282	195
Greater than ten years	31	0
Asset-backed securities	0	0
Fair Value	$ 1,343	$ 1,217