Investments (Short-Term and Long-Term Investments) (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 45,926	$ 39,669
Securities, Available for sale Debt Securities, Gross Unrealized Gains	59	822
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(3,664)	(274)
Debt Securities, Available-for-sale	42,321	40,217
Held-to-maturity securities, Amortized Cost	696	641
Securities, Held to maturity, Unrecognized Holding Gain	0	4
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(17)	(2)
Debt Securities, Held-to-maturity, Fair Value	679	643
Total investments, Amortized Cost	46,622	40,310
Total investments, Gross Unrealized Gains	59	826
Total investments, Gross Unrealized Losses	(3,681)	(276)
Investments, Fair Value Disclosure	43,000	40,860
Debt Securities - held-to-maturity
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale	42,321	40,217
U.S. Government and Agency Obligations [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	4,093	3,206
Securities, Available for sale Debt Securities, Gross Unrealized Gains	1	23
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(285)	(31)
Debt Securities, Available-for-sale	3,809	3,198
Held-to-maturity securities, Amortized Cost	578	511
Securities, Held to maturity, Unrecognized Holding Gain	0	2
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(14)	(2)
Debt Securities, Held-to-maturity, Fair Value	564	511
State and Municipal Obligations [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	7,702	6,829
Securities, Available for sale Debt Securities, Gross Unrealized Gains	25	297
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(479)	(20)
Debt Securities, Available-for-sale	7,248	7,106
Held-to-maturity securities, Amortized Cost	29	30
Securities, Held to maturity, Unrecognized Holding Gain	0	2
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(3)	0
Debt Securities, Held-to-maturity, Fair Value	26	32
Corporate Obligations [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	23,675	20,947
Securities, Available for sale Debt Securities, Gross Unrealized Gains	17	372
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(1,798)	(145)
Debt Securities, Available-for-sale	21,894	21,174
Held-to-maturity securities, Amortized Cost	89	100
Securities, Held to maturity, Unrecognized Holding Gain	0	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	0	0
Debt Securities, Held-to-maturity, Fair Value	89	100
U.S. Agency Mortgage-Backed Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	7,379	5,868
Securities, Available for sale Debt Securities, Gross Unrealized Gains	15	88
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(808)	(55)
Debt Securities, Available-for-sale	6,586	5,901
Non-U.S. Agency Mortgage-Backed Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	3,077	2,819
Securities, Available for sale Debt Securities, Gross Unrealized Gains	1	42
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(294)	(23)
Debt Securities, Available-for-sale	$ 2,784	$ 2,838

Investments at amortized cost.

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