Lending Activities - Credit Quality Performance Indicators for Commercial Mortgages (Details) $ in Millions	Sep. 30, 2025 USD ($) loan	Jun. 30, 2025 USD ($)	Dec. 31, 2024 USD ($) loan	Sep. 30, 2024 USD ($)	Jun. 30, 2024 USD ($)	Dec. 31, 2023 USD ($)
Financing Receivable, Credit Quality Indicator [Line Items]
Allowance for credit losses	$ 37,740		$ 37,800
Commercial mortgage loans
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans | loan	162		190
Total	$ 2,869		$ 3,305
Allowance for credit losses	$ 104	$ 106	$ 163	$ 165	$ 162	$ 138
Percent of Total	100.00%		100.00%
Percentage of total, allowance for credit losses	4.00%		5.00%
Commercial mortgage loans | In good standing
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans | loan	158		186
Total	$ 2,779		$ 3,106
Percent of Total	97.00%		94.00%
Commercial mortgage loans | 90 days or less delinquent
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans | loan	0		1
Total	$ 0		$ 25
Percent of Total	0.00%		1.00%
Commercial mortgage loans | >90 days delinquent or in process of foreclosure
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans | loan	4		3
Total	$ 90		$ 174
Percent of Total	3.00%		5.00%
Commercial mortgage loans | Apartments
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 908		$ 1,087
Allowance for credit losses	1		5
Commercial mortgage loans | Apartments | In good standing
Financing Receivable, Credit Quality Indicator [Line Items]
Total	908		1,087
Commercial mortgage loans | Apartments | 90 days or less delinquent
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0		0
Commercial mortgage loans | Apartments | >90 days delinquent or in process of foreclosure
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0		0
Commercial mortgage loans | Offices
Financing Receivable, Credit Quality Indicator [Line Items]
Total	1,033		1,108
Allowance for credit losses	59		99
Commercial mortgage loans | Offices | In good standing
Financing Receivable, Credit Quality Indicator [Line Items]
Total	1,004		971
Commercial mortgage loans | Offices | 90 days or less delinquent
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0		25
Commercial mortgage loans | Offices | >90 days delinquent or in process of foreclosure
Financing Receivable, Credit Quality Indicator [Line Items]
Total	29		112
Commercial mortgage loans | Retail
Financing Receivable, Credit Quality Indicator [Line Items]
Total	391		432
Allowance for credit losses	33		34
Commercial mortgage loans | Retail | In good standing
Financing Receivable, Credit Quality Indicator [Line Items]
Total	330		370
Commercial mortgage loans | Retail | 90 days or less delinquent
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0		0
Commercial mortgage loans | Retail | >90 days delinquent or in process of foreclosure
Financing Receivable, Credit Quality Indicator [Line Items]
Total	61		62
Commercial mortgage loans | Industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Total	208		301
Allowance for credit losses	1		11
Commercial mortgage loans | Industrial | In good standing
Financing Receivable, Credit Quality Indicator [Line Items]
Total	208		301
Commercial mortgage loans | Industrial | 90 days or less delinquent
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0		0
Commercial mortgage loans | Industrial | >90 days delinquent or in process of foreclosure
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0		0
Commercial mortgage loans | Hotel
Financing Receivable, Credit Quality Indicator [Line Items]
Total	203		258
Allowance for credit losses	10		13
Commercial mortgage loans | Hotel | In good standing
Financing Receivable, Credit Quality Indicator [Line Items]
Total	203		258
Commercial mortgage loans | Hotel | 90 days or less delinquent
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0		0
Commercial mortgage loans | Hotel | >90 days delinquent or in process of foreclosure
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0		0
Commercial mortgage loans | Others
Financing Receivable, Credit Quality Indicator [Line Items]
Total	126		119
Allowance for credit losses	0		1
Commercial mortgage loans | Others | In good standing
Financing Receivable, Credit Quality Indicator [Line Items]
Total	126		119
Commercial mortgage loans | Others | 90 days or less delinquent
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0		0
Commercial mortgage loans | Others | >90 days delinquent or in process of foreclosure
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 0		$ 0