Fair Value Measurements (Carrying Values And Fair Values Of Financial Instruments Not Measured At Fair Value) (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fixed maturities, held-to-maturity, fair value	$ 0	$ 8,439
Fixed maturities, held-to-maturity		8,882
Private debt held-for-investment	2,553	0
Total assets (preliminary)	230,682	199,017
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Repurchase agreements	2,833	1,419
Short-term debt	1,460	475
Long-term debt	13,035	14,402
Total liabilities	166,991	148,498
Cost
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fixed maturities, held-to-maturity		8,848
Private debt held-for-investment	2,553
Total assets (preliminary)	2,553
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Repurchase agreements	2,833	1,419
Short-term debt	1,460	475
Long-term debt	13,035	14,402
Trust preferred securities	308	308
Total liabilities	17,636	16,604
Level 1 | Portion at Other than Fair Value Measurement
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fixed maturities, held-to-maturity, fair value		1,299
Private debt held-for-investment	0
Total assets (preliminary)	0
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Repurchase agreements	0	0
Short-term debt, Fair Value	0	0
Long-term debt, Fair Value	0	0
Trust preferred securities	0	0
Total liabilities	0	0
Level 2 | Portion at Other than Fair Value Measurement
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fixed maturities, held-to-maturity, fair value		7,140
Private debt held-for-investment	0
Total assets (preliminary)	0
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Repurchase agreements	2,833	1,419
Short-term debt, Fair Value	1,431	473
Long-term debt, Fair Value	11,924	12,495
Trust preferred securities	365	383
Total liabilities	16,553	14,770
Level 3 | Portion at Other than Fair Value Measurement
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fixed maturities, held-to-maturity, fair value		0
Private debt held-for-investment	2,560
Total assets (preliminary)	2,560
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Repurchase agreements	0	0
Short-term debt, Fair Value	0	0
Long-term debt, Fair Value	0	0
Trust preferred securities	0	0
Total liabilities	0	0
Fair Value, Inputs, Level 1, Level 2, and Level 3 | Portion at Other than Fair Value Measurement
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fixed maturities, held-to-maturity, fair value		8,439
Private debt held-for-investment	2,560
Total assets (preliminary)	2,560
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Repurchase agreements	2,833	1,419
Short-term debt, Fair Value	1,431	473
Long-term debt, Fair Value	11,924	12,495
Trust preferred securities	365	383
Total liabilities	$ 16,553	14,770
U.S. Treasury / Agency
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fixed maturities, held-to-maturity, fair value		1,370
Fixed maturities, held-to-maturity		1,417
U.S. Treasury / Agency | Cost
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fixed maturities, held-to-maturity		1,417
U.S. Treasury / Agency | Level 1 | Portion at Other than Fair Value Measurement
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fixed maturities, held-to-maturity, fair value		1,299
U.S. Treasury / Agency | Level 2 | Portion at Other than Fair Value Measurement
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fixed maturities, held-to-maturity, fair value		71
U.S. Treasury / Agency | Level 3 | Portion at Other than Fair Value Measurement
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fixed maturities, held-to-maturity, fair value		0
U.S. Treasury / Agency | Fair Value, Inputs, Level 1, Level 2, and Level 3 | Portion at Other than Fair Value Measurement
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fixed maturities, held-to-maturity, fair value		1,370
Non-U.S.
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fixed maturities, held-to-maturity, fair value		1,054
Fixed maturities, held-to-maturity		1,140
Non-U.S. | Cost
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fixed maturities, held-to-maturity		1,136
Non-U.S. | Level 1 | Portion at Other than Fair Value Measurement
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fixed maturities, held-to-maturity, fair value		0
Non-U.S. | Level 2 | Portion at Other than Fair Value Measurement
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fixed maturities, held-to-maturity, fair value		1,054
Non-U.S. | Level 3 | Portion at Other than Fair Value Measurement
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fixed maturities, held-to-maturity, fair value		0
Non-U.S. | Fair Value, Inputs, Level 1, Level 2, and Level 3 | Portion at Other than Fair Value Measurement
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fixed maturities, held-to-maturity, fair value		1,054
Corporate and asset-backed securities
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fixed maturities, held-to-maturity, fair value		1,580
Fixed maturities, held-to-maturity		1,733
Corporate and asset-backed securities | Cost
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fixed maturities, held-to-maturity		1,705
Corporate and asset-backed securities | Level 1 | Portion at Other than Fair Value Measurement
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fixed maturities, held-to-maturity, fair value		0
Corporate and asset-backed securities | Level 2 | Portion at Other than Fair Value Measurement
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fixed maturities, held-to-maturity, fair value		1,580
Corporate and asset-backed securities | Level 3 | Portion at Other than Fair Value Measurement
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fixed maturities, held-to-maturity, fair value		0
Corporate and asset-backed securities | Fair Value, Inputs, Level 1, Level 2, and Level 3 | Portion at Other than Fair Value Measurement
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fixed maturities, held-to-maturity, fair value		1,580
Mortgage-backed securities
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fixed maturities, held-to-maturity, fair value		1,351
Fixed maturities, held-to-maturity		1,456
Mortgage-backed securities | Cost
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fixed maturities, held-to-maturity		1,455
Mortgage-backed securities | Level 1 | Portion at Other than Fair Value Measurement
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fixed maturities, held-to-maturity, fair value		0
Mortgage-backed securities | Level 2 | Portion at Other than Fair Value Measurement
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fixed maturities, held-to-maturity, fair value		1,351
Mortgage-backed securities | Level 3 | Portion at Other than Fair Value Measurement
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fixed maturities, held-to-maturity, fair value		0
Mortgage-backed securities | Fair Value, Inputs, Level 1, Level 2, and Level 3 | Portion at Other than Fair Value Measurement
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fixed maturities, held-to-maturity, fair value		1,351
Municipal
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fixed maturities, held-to-maturity, fair value		3,084
Fixed maturities, held-to-maturity		3,136
Municipal | Cost
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fixed maturities, held-to-maturity		3,135
Municipal | Level 1 | Portion at Other than Fair Value Measurement
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fixed maturities, held-to-maturity, fair value		0
Municipal | Level 2 | Portion at Other than Fair Value Measurement
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fixed maturities, held-to-maturity, fair value		3,084
Municipal | Level 3 | Portion at Other than Fair Value Measurement
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fixed maturities, held-to-maturity, fair value		0
Municipal | Fair Value, Inputs, Level 1, Level 2, and Level 3 | Portion at Other than Fair Value Measurement
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fixed maturities, held-to-maturity, fair value		$ 3,084