Lending Activities - Credit quality performance indicators for commercial mortgages (Details) $ in Millions	Mar. 31, 2023 USD ($) loan	Dec. 31, 2022 USD ($) loan	Mar. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 51,616	$ 50,321
Allowance for credit losses	$ 38,421	$ 38,351
Commercial mortgage loans
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans | loan	627	629
Total	$ 37,779	$ 37,128
Allowance for credit losses	$ 706	$ 640	$ 533	$ 545
Percent of Total	100.00%	100.00%
Percentage of total, allowance for credit losses	2.00%	2.00%
Commercial mortgage loans | In good standing
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans | loan	621	625
Total	$ 37,209	$ 36,913
Percent of Total	98.00%	99.00%
Commercial mortgage loans | 90 days or less delinquent
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans | loan	2	0
Total	$ 360	$ 0
Percent of Total	1.00%	0.00%
Commercial mortgage loans | >90 days delinquent or in process of foreclosure
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans | loan	4	4
Total	$ 210	$ 215
Percent of Total	1.00%	1.00%
Commercial mortgage loans | Apartments
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 14,968	$ 14,597
Allowance for credit losses	101	100
Commercial mortgage loans | Apartments | In good standing
Financing Receivable, Credit Quality Indicator [Line Items]
Total	14,608	14,597
Commercial mortgage loans | Apartments | 90 days or less delinquent
Financing Receivable, Credit Quality Indicator [Line Items]
Total	360	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	10,119	10,275
Allowance for credit losses	411	351
Commercial mortgage loans | Offices | In good standing
Financing Receivable, Credit Quality Indicator [Line Items]
Total	9,950	10,102
Commercial mortgage loans | Offices | 90 days or less delinquent
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0	0
Commercial mortgage loans | Offices | >90 days delinquent or in process of foreclosure
Financing Receivable, Credit Quality Indicator [Line Items]
Total	169	173
Commercial mortgage loans | Retail
Financing Receivable, Credit Quality Indicator [Line Items]
Total	4,131	3,816
Allowance for credit losses	87	81
Commercial mortgage loans | Retail | In good standing
Financing Receivable, Credit Quality Indicator [Line Items]
Total	4,090	3,774
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	41	42
Commercial mortgage loans | Industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Total	6,062	6,006
Allowance for credit losses	72	71
Commercial mortgage loans | Industrial | In good standing
Financing Receivable, Credit Quality Indicator [Line Items]
Total	6,062	6,006
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	2,082	2,027
Allowance for credit losses	27	29
Commercial mortgage loans | Hotel | In good standing
Financing Receivable, Credit Quality Indicator [Line Items]
Total	2,082	2,027
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	417	407
Allowance for credit losses	8	8
Commercial mortgage loans | Others | In good standing
Financing Receivable, Credit Quality Indicator [Line Items]
Total	417	407
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