Unpaid Claims and Claims Expense Short Duration Contracts (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023	Dec. 31, 2022
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Liability for Claims and Claims Adjustment Expense	$ 2,753	$ 2,558	$ 2,730	$ 2,480
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	(75)	(67)	(80)	(57)
Liability For Unpaid Claims And Claims Adjustment Expense Net Of Recoverable	2,678	2,491	$ 2,650	$ 2,423
Current Year Claims and Claims Adjustment Expense	399	363
Prior Year Claims and Claims Adjustment Expense	(28)	(25)
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims	371	338
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Current Year	(19)	(23)
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years	(290)	(249)
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid	(309)	(272)
Interest On Liability For Policy And Contract Claims	10	8
Liability for Unpaid Claims and Claims Adjustment Expense, Foreign Currency Translation Gain (Loss)	(44)	(6)
Liability for Unpaid Claims and Claims Adjustment Expense Other	$ (34)	$ (2)