Debt Service Coverage Ratio for Fixed Rate Commercial Mortgage Loans by Property Type (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Jun. 30, 2022	Dec. 31, 2021
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	$ 7,088	$ 6,856
% 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	$ 7,088	$ 6,856
% of total	100.00%	100.00%
Weighted-average debt-to-value	56.00%	55.00%
Retail
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	$ 2,901	$ 2,774
% of total	41.00%	40.00%
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	$ 2,901	$ 2,774
Industrial
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	$ 1,532	$ 1,420
% of total	22.00%	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	$ 1,532	$ 1,420
Office
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	$ 1,512	$ 1,526
% of total	21.00%	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	$ 1,512	$ 1,526
Apartments
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	$ 578	$ 585
% of total	8.00%	9.00%
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	$ 578	$ 585
Mixed Use
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	$ 350	$ 330
% 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	$ 350	$ 330
Other
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans, amortized cost	$ 215	$ 221
% of total	3.00%	3.00%
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	$ 215	$ 221
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	$ 183	$ 223
% of total	3.00%	3.00%
Weighted-average debt-to-value	60.00%	68.00%
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	$ 94	$ 102
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	6	9
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	38	67
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	17	17
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	23	24
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	5	4
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	$ 526	$ 559
% of total	7.00%	8.00%
Weighted-average debt-to-value	60.00%	61.00%
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	$ 150	$ 166
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	76	64
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	106	109
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	62	62
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	31	32
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	101	126
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	$ 903	$ 791
% of total	13.00%	12.00%
Weighted-average debt-to-value	63.00%	61.00%
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	$ 429	$ 405
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	134	82
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	179	167
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	84	84
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	40	40
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	37	13
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	$ 3,242	$ 2,958
% of total	46.00%	43.00%
Weighted-average debt-to-value	61.00%	60.00%
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	$ 1,534	$ 1,375
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	663	599
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	630	593
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	239	225
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	137	118
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	39	48
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	$ 2,234	$ 2,325
% of total	31.00%	34.00%
Weighted-average debt-to-value	44.00%	43.00%
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	$ 694	$ 726
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	653	666
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	559	590
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	176	197
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	119	116
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	$ 33	$ 30