Schedule IV - Reinsurance (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Gross Amount		$ 9,652	$ 8,542	$ 7,707
Ceded to other Companies		(4,935)	(4,249)	(3,735)
Assumed From Other Companies		8,751	6,785	5,045
Net Amount		$ 13,468	$ 11,078	$ 9,017
Percentage of Amount Assumed to Net		65.00%	61.20%	55.90%
Operating segments | Insurance
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Gross Amount		$ 7,865	$ 6,889	$ 5,834
Ceded to other Companies	[1],[2]	(2,049)	(1,910)	(1,719)
Assumed From Other Companies	[1]	46	42	34
Net Amount		$ 5,862	$ 5,021	$ 4,149
Percentage of Amount Assumed to Net		0.80%	0.80%	0.80%
Operating segments | Reinsurance
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Gross Amount		$ 626	$ 397	$ 409
Ceded to other Companies	[1],[2]	(2,559)	(2,024)	(1,840)
Assumed From Other Companies	[1]	8,487	6,553	4,685
Net Amount		$ 6,554	$ 4,924	$ 3,254
Percentage of Amount Assumed to Net		129.50%	133.10%	144.00%
Operating segments | Mortgage
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Gross Amount		$ 1,161	$ 1,256	$ 1,213
Ceded to other Companies	[1],[2]	(335)	(322)	(247)
Assumed From Other Companies	[1]	226	199	294
Net Amount		$ 1,052	$ 1,133	$ 1,261
Percentage of Amount Assumed to Net		21.50%	17.60%	23.30%
Operating segments | Other
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Gross Amount				$ 251
Ceded to other Companies	[2]	$ 0	$ 0	(105)	[1]
Assumed From Other Companies	[1]			206
Net Amount		$ 0	$ 0	$ 353
Percentage of Amount Assumed to Net				58.40%

[1] Certain amounts included in the gross premiums written of each segment are related to intersegment transactions and are included in the gross premiums written of each segment. Accordingly, the sum of gross premiums written for each segment does not agree to the total gross premiums written as shown in the table above due to the elimination of intersegment transactions in the total.

[2] Certain assumed and ceded amounts related to intersegment transactions are included in individual segment results. Accordingly, the sum of such transactions for each segment does not agree to the total due to eliminations.