Investments in debt and equity securities - Cost basis and fair value of the available-for-sale debt securities by contractual maturity (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Cost Basis
Due in one year or less	$ 1,274
Due after one year through five years	1,820
Due after five years through ten years	304
Due after ten years	102
Cost Basis	4,114	$ 3,871
Fair Value
Due in one year or less	1,270
Due after one year through five years	1,794
Due after five years through ten years	301
Due after ten years	102
Fair Value	4,042	3,797
U.S. governmental agency
Cost Basis
Cost Basis	476	433
Fair Value
Fair Value	443	410
Residential
Cost Basis
Cost Basis	2	3
Fair Value
Fair Value	2	2
Commercial
Cost Basis
Cost Basis	136	137
Fair Value
Fair Value	$ 130	$ 128