Fair Value - Rollforward of Level 3 assets and liabilities (Details) - Recurring - USD ($) $ in Millions		3 Months Ended				6 Months Ended
		Jun. 30, 2024		Jun. 30, 2023		Jun. 30, 2024	Jun. 30, 2023
Other liabilities
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period		$ (22)		$ (14)		$ (22)	$ (14)
Total gains or (losses) (realized/unrealized) - included in earnings	[1]	0		0		(1)	0
Total gains or (losses) (realized/unrealized) - included in other comprehensive income		0		0		1	0
Purchases, issuances, sales and settlements
Purchases		0		0		0	0
Issuances		(13)		(5)		(13)	(5)
Sales		0		0		0	0
Settlements		0		0		0	0
Transfers in and/or out of Level 3		0		0		0	0
Balance at end of period		(35)		(19)		(35)	(19)
Available for sale | Corporate bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period		160		69		147	121
Total gains or (losses) (realized/unrealized) - included in earnings	[1]	0		0		0	1
Total gains or (losses) (realized/unrealized) - included in other comprehensive income		0		0		2	0
Purchases, issuances, sales and settlements
Purchases		0		43		98	43
Issuances		0		0		0	0
Sales		0		0		0	0
Settlements		0		(12)		(87)	(65)
Transfers in and/or out of Level 3		0		0		0	0
Balance at end of period		160		100		160	100
Available for sale | Short-term investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period		97		0		84	0
Total gains or (losses) (realized/unrealized) - included in earnings		0	[1]	0	[1]	0	0
Total gains or (losses) (realized/unrealized) - included in other comprehensive income		0		0		1	0
Purchases, issuances, sales and settlements
Purchases		0		0		12	0
Issuances		0		0		0	0
Sales		0		0		0	0
Settlements		0		0		0	0
Transfers in and/or out of Level 3		0		0		0	0
Balance at end of period		97		0		97	0
Fair value option | Other investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period		126		46		106	33
Total gains or (losses) (realized/unrealized) - included in earnings	[1]	0		0		(4)	(1)
Total gains or (losses) (realized/unrealized) - included in other comprehensive income		0		0		0	0
Purchases, issuances, sales and settlements
Purchases		30		40		60	58
Issuances		0		0		0	0
Sales		(2)		0		(2)	(4)
Settlements		(10)		0		(16)	0
Transfers in and/or out of Level 3		0		0		0	0
Balance at end of period		144		86		144	86
Fair value option | Short term investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period		17		0		10	0
Total gains or (losses) (realized/unrealized) - included in earnings	[1]	0		0		0	0
Total gains or (losses) (realized/unrealized) - included in other comprehensive income		0		0		0	0
Purchases, issuances, sales and settlements
Purchases		3		0		10	0
Issuances		0		0		0	0
Sales		0		0		0	0
Settlements		(6)		0		(6)	0
Transfers in and/or out of Level 3		0		0		0	0
Balance at end of period		14		0		14	0
Fair value option | Equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period		4		4		4	4
Total gains or (losses) (realized/unrealized) - included in earnings	[1]	0		0		0	0
Total gains or (losses) (realized/unrealized) - included in other comprehensive income		0		0		0	0
Purchases, issuances, sales and settlements
Purchases		0		0		0	0
Issuances		0		0		0	0
Sales		0		0		0	0
Settlements		0		0		0	0
Transfers in and/or out of Level 3		0		0		0	0
Balance at end of period		4		4		4	4
Equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period		5		5		5	4
Total gains or (losses) (realized/unrealized) - included in earnings	[1]	0		0		0	0
Total gains or (losses) (realized/unrealized) - included in other comprehensive income		0		0		0	0
Purchases, issuances, sales and settlements
Purchases		1		0		1	1
Issuances		0		0		0	0
Sales		0		0		0	0
Settlements		0		0		0	0
Transfers in and/or out of Level 3		0		0		0	0
Balance at end of period		$ 6		$ 5		$ 6	$ 5

[1] Gains or losses were included in net realized gains (losses).