Investments - Summary of Debt Securities with a Decline in Fair Value (Details) $ in Millions	Mar. 31, 2025 USD ($) position
Total
Fair Value	$ 4,930
Total Amortized Cost	5,488
Unrealized Depreciation	$ (558)
Number of Issues \| position	2,342
Investment grade \| Debt securities
One year or less
Fair Value	$ 567
Amortized Cost	573
Unrealized Depreciation	$ (6)
Number of Issues \| position	353
More than one year
Fair Value	$ 3,818
Amortized Cost	4,319
Unrealized Depreciation	$ (501)
Number of Issues \| position	1,080
Below investment grade \| Debt securities
One year or less
Fair Value	$ 220
Amortized Cost	228
Unrealized Depreciation	$ (8)
Number of Issues \| position	802
More than one year
Fair Value	$ 325
Amortized Cost	368
Unrealized Depreciation	$ (43)
Number of Issues \| position	107

Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months Or Longer

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