Financial Instruments - Gross Unrealized Losses and Fair Values for Investments in Unrealized Loss Position (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Investments, Unrealized Loss Position [Line Items]
Less than 12 Months, Fair Value	$ 6,077	$ 20,569
Less than 12 Months, Unrealized Loss	(68)	(249)
12 Months or Greater, Fair Value	8,484	13,227
12 Months or Greater, Unrealized Loss	(269)	(535)
Total Fair Value	14,561	33,796
Total Unrealized Loss	(337)	(784)
Government bonds
Investments, Unrealized Loss Position [Line Items]
Less than 12 Months, Fair Value	2,391	11,119
Less than 12 Months, Unrealized Loss	(19)	(126)
12 Months or Greater, Fair Value	1,370	2,576
12 Months or Greater, Unrealized Loss	(29)	(88)
Total Fair Value	3,761	13,695
Total Unrealized Loss	(48)	(214)
Corporate debt securities
Investments, Unrealized Loss Position [Line Items]
Less than 12 Months, Fair Value	1,020	4,228
Less than 12 Months, Unrealized Loss	(1)	(17)
12 Months or Greater, Fair Value	4,247	6,838
12 Months or Greater, Unrealized Loss	(73)	(168)
Total Fair Value	5,267	11,066
Total Unrealized Loss	(74)	(185)
Mortgage-backed and asset-backed securities
Investments, Unrealized Loss Position [Line Items]
Less than 12 Months, Fair Value	2,666	5,222
Less than 12 Months, Unrealized Loss	(48)	(106)
12 Months or Greater, Fair Value	2,867	3,813
12 Months or Greater, Unrealized Loss	(167)	(279)
Total Fair Value	5,533	9,035
Total Unrealized Loss	$ (215)	$ (385)