Debt Service Coverage Ratio for Fixed Rate Commercial Mortgage Loans by Property Type (Detail) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2024	Dec. 31, 2023
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	$ 6,692	$ 6,829
% of total	100.00%	100.00%
Fixed Rate Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	$ 6,692	$ 6,829
% of total	100.00%	100.00%
Weighted-average debt-to-value	55.00%	55.00%
Retail
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	$ 2,794	$ 2,858
% of total	42.00%	42.00%
Retail | Fixed Rate Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	$ 2,794	$ 2,858
Industrial
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	$ 1,400	$ 1,440
% of total	21.00%	21.00%
Industrial | Fixed Rate Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	$ 1,400	$ 1,440
Office
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	$ 1,457	$ 1,481
% of total	22.00%	22.00%
Office | Fixed Rate Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	$ 1,457	$ 1,481
Apartments
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	$ 513	$ 522
% of total	8.00%	8.00%
Apartments | Fixed Rate Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	$ 513	$ 522
Mixed Use
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	$ 372	$ 371
% of total	5.00%	5.00%
Mixed Use | Fixed Rate Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	$ 372	$ 371
Other
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	$ 156	$ 157
% of total	2.00%	2.00%
Other | Fixed Rate Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	$ 156	$ 157
Less than 1.00 | Fixed Rate Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	$ 253	$ 265
% of total	4.00%	4.00%
Weighted-average debt-to-value	63.00%	64.00%
Less than 1.00 | Retail | Fixed Rate Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	$ 49	$ 54
Less than 1.00 | Industrial | Fixed Rate Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	42	43
Less than 1.00 | Office | Fixed Rate Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	99	105
Less than 1.00 | Apartments | Fixed Rate Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	12	12
Less than 1.00 | Mixed Use | Fixed Rate Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	27	27
Less than 1.00 | Other | Fixed Rate Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	24	24
1.00 - 1.25 | Fixed Rate Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	$ 255	$ 263
% of total	4.00%	4.00%
Weighted-average debt-to-value	62.00%	63.00%
1.00 - 1.25 | Retail | Fixed Rate Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	$ 106	$ 105
1.00 - 1.25 | Industrial | Fixed Rate Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	30	30
1.00 - 1.25 | Office | Fixed Rate Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	45	48
1.00 - 1.25 | Apartments | Fixed Rate Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	50	51
1.00 - 1.25 | Mixed Use | Fixed Rate Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	10	14
1.00 - 1.25 | Other | Fixed Rate Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	14	15
1.26 - 1.50 | Fixed Rate Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	$ 1,223	$ 1,196
% of total	18.00%	17.00%
Weighted-average debt-to-value	64.00%	65.00%
1.26 - 1.50 | Retail | Fixed Rate Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	$ 578	$ 583
1.26 - 1.50 | Industrial | Fixed Rate Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	209	181
1.26 - 1.50 | Office | Fixed Rate Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	244	244
1.26 - 1.50 | Apartments | Fixed Rate Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	79	86
1.26 - 1.50 | Mixed Use | Fixed Rate Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	91	80
1.26 - 1.50 | Other | Fixed Rate Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	22	22
1.51 - 2.00 | Fixed Rate Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	$ 2,569	$ 2,611
% of total	38.00%	38.00%
Weighted-average debt-to-value	57.00%	58.00%
1.51 - 2.00 | Retail | Fixed Rate Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	$ 1,120	$ 1,142
1.51 - 2.00 | Industrial | Fixed Rate Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	472	471
1.51 - 2.00 | Office | Fixed Rate Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	601	615
1.51 - 2.00 | Apartments | Fixed Rate Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	184	187
1.51 - 2.00 | Mixed Use | Fixed Rate Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	161	164
1.51 - 2.00 | Other | Fixed Rate Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	31	32
Greater than 2.00 | Fixed Rate Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	$ 2,392	$ 2,494
% of total	36.00%	37.00%
Weighted-average debt-to-value	46.00%	46.00%
Greater than 2.00 | Retail | Fixed Rate Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	$ 941	$ 974
Greater than 2.00 | Industrial | Fixed Rate Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	647	715
Greater than 2.00 | Office | Fixed Rate Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	468	469
Greater than 2.00 | Apartments | Fixed Rate Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	188	186
Greater than 2.00 | Mixed Use | Fixed Rate Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	83	86
Greater than 2.00 | Other | Fixed Rate Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	$ 65	$ 64