Schedule IV - Reinsurance (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Gross Amount		$ 10,056	$ 9,652	$ 8,542
Ceded to other Companies		(5,779)	(4,935)	(4,249)
Assumed From Other Companies		11,455	8,751	6,785
Net Amount		$ 15,732	$ 13,468	$ 11,078
Percentage of Amount Assumed to Net		72.80%	65.00%	61.20%
Operating segments | Insurance
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Gross Amount		$ 7,970	$ 7,865	$ 6,889
Ceded to other Companies	[1],[2]	(2,179)	(2,049)	(1,910)
Assumed From Other Companies	[1]	1,083	46	42
Net Amount		$ 6,874	$ 5,862	$ 5,021
Percentage of Amount Assumed to Net		15.80%	0.80%	0.80%
Operating segments | Reinsurance
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Gross Amount		$ 956	$ 626	$ 397
Ceded to other Companies	[1],[2]	(3,366)	(2,559)	(2,024)
Assumed From Other Companies	[1]	10,156	8,487	6,553
Net Amount		$ 7,746	$ 6,554	$ 4,924
Percentage of Amount Assumed to Net		131.10%	129.50%	133.10%
Operating segments | Mortgage
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Gross Amount		$ 1,130	$ 1,161	$ 1,256
Ceded to other Companies	[1],[2]	(239)	(335)	(322)
Assumed From Other Companies	[1]	221	226	199
Net Amount		$ 1,112	$ 1,052	$ 1,133
Percentage of Amount Assumed to Net		19.90%	21.50%	17.60%

[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.