Fair Value Measurements - Changes in Level 3 Financial Assets and Financial Liabilities Carried at Fair Value (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Transfers into / (out of) Level 3
Change in unrealized gain or (loss) included in Other comprehensive loss for assets held at the end of the reporting period	$ 4	$ (2)	$ 7	$ (6)
Debt and Equity Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	373
Beginning balance, including held for sale assets		422	417	447
Losses included in Shareholders' net income	(4)	(40)	(14)	(61)
Gains (losses) included in Other comprehensive loss	3	(2)	10	(5)
Purchases, sales and settlements
Purchases	25	11	27	11
Sales	(2)	0	(2)	0
Settlements	(49)	(1)	(80)	(15)
Total purchases, sales and settlements	(26)	10	(55)	(4)
Transfers into / (out of) Level 3
Transfers into Level 3	31	15	49	31
Transfers out of Level 3	(15)	(8)	(45)	(11)
Total transfers into / (out of) Level 3	16	7	4	20
Ending balance	362		362
Ending balance, including held for sale assets		397		397
Total losses included in Shareholders' net income attributable to instruments held at the reporting date	$ (4)	$ (41)	$ (17)	$ (61)