Investments in debt and equity securities - Available-for-sale debt securities in an unrealized loss position (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Less than 12 months
Fair Value	$ 875	$ 809
Unrealized Losses	6	0
12 months or more
Fair Value	1,290	1,541
Unrealized Losses	75	85
Total - Fair Value	2,165	2,350
Total - Unrealized losses	81	85
Other U.S. and non-U.S. government bonds
Less than 12 months
Fair Value	0	0
Unrealized Losses	0	0
12 months or more
Fair Value	55	25
Unrealized Losses	4	3
Total - Fair Value	55	25
Total - Unrealized losses	4	3
Corporate bonds and other debt securities
Less than 12 months
Fair Value	729	765
Unrealized Losses	3	0
12 months or more
Fair Value	812	1,011
Unrealized Losses	33	45
Total - Fair Value	1,541	1,776
Total - Unrealized losses	36	45
Asset-backed securities
Less than 12 months
Fair Value	7	9
Unrealized Losses	0	0
12 months or more
Fair Value	37	97
Unrealized Losses	2	3
Total - Fair Value	44	106
Total - Unrealized losses	2	3
U.S. governmental agency
Less than 12 months
Fair Value	126	33
Unrealized Losses	3	0
12 months or more
Fair Value	273	287
Unrealized Losses	30	25
Total - Fair Value	399	320
Total - Unrealized losses	33	25
Commercial
Less than 12 months
Fair Value	13	2
Unrealized Losses	0	0
12 months or more
Fair Value	113	121
Unrealized Losses	6	9
Total - Fair Value	126	123
Total - Unrealized losses	$ 6	$ 9