Investments - Investments - Loan-to-Value and Debt Service Coverage Ratio by Origination Year (Details) $ in Millions	Mar. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Mar. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Schedule of Investments [Line Items]
Current Weighted Average Loan to Value Ratio of Commercial Mortgage Loan	55.00%
Original Weighted Average Loan to Value Ratio of Commercial Mortgage loan	59.00%
Commercial Loan [Member]
Schedule of Investments [Line Items]
Avg. Debt-Service Coverage Ratio	2.60	2.60
Financing Receivable, before Allowance for Credit Loss	$ 6,245	$ 6,138
Financing Receivable, Allowance for Credit Loss	$ 48	$ 51	$ 36	$ 36
Commercial Loan [Member] | Originated in Current Fiscal Year
Schedule of Investments [Line Items]
Avg. Debt-Service Coverage Ratio	1.62	1.47
Commercial Loan [Member] | Originated in Fiscal Year Before Latest Fiscal Year
Schedule of Investments [Line Items]
Avg. Debt-Service Coverage Ratio	1.45	2.60
Commercial Loan [Member] | Originated Two Years Before Latest Fiscal Year
Schedule of Investments [Line Items]
Avg. Debt-Service Coverage Ratio	2.63	2.78
Commercial Loan [Member] | Originated Three Years Before Latest Fiscal Year
Schedule of Investments [Line Items]
Avg. Debt-Service Coverage Ratio	2.84	3.00
Commercial Loan [Member] | Originated Four Years Before Latest Fiscal Year
Schedule of Investments [Line Items]
Avg. Debt-Service Coverage Ratio	2.99	2.76
Commercial Loan [Member] | Originated Five or More Years Before Latest Fiscal Year
Schedule of Investments [Line Items]
Avg. Debt-Service Coverage Ratio	2.57	2.47
Commercial Loan [Member] | LTV Greater than 80 Percent
Schedule of Investments [Line Items]
Avg. Debt-Service Coverage Ratio	0.95	1.29
Commercial Loan [Member] | LTV Greater than 80 Percent | Originated in Current Fiscal Year
Schedule of Investments [Line Items]
Avg. Debt-Service Coverage Ratio	0	0
Commercial Loan [Member] | LTV Greater than 80 Percent | Originated in Fiscal Year Before Latest Fiscal Year
Schedule of Investments [Line Items]
Avg. Debt-Service Coverage Ratio	0	1.09
Commercial Loan [Member] | LTV Greater than 80 Percent | Originated Two Years Before Latest Fiscal Year
Schedule of Investments [Line Items]
Avg. Debt-Service Coverage Ratio	1.14	1.05
Commercial Loan [Member] | LTV Greater than 80 Percent | Originated Three Years Before Latest Fiscal Year
Schedule of Investments [Line Items]
Avg. Debt-Service Coverage Ratio	1.05	0
Commercial Loan [Member] | LTV Greater than 80 Percent | Originated Four Years Before Latest Fiscal Year
Schedule of Investments [Line Items]
Avg. Debt-Service Coverage Ratio	0	0
Commercial Loan [Member] | LTV Greater than 80 Percent | Originated Five or More Years Before Latest Fiscal Year
Schedule of Investments [Line Items]
Avg. Debt-Service Coverage Ratio	0.89	1.41
Commercial Loan [Member] | 65% - 80%
Schedule of Investments [Line Items]
Avg. Debt-Service Coverage Ratio	2.24	2.25
Commercial Loan [Member] | 65% - 80% | Originated in Current Fiscal Year
Schedule of Investments [Line Items]
Avg. Debt-Service Coverage Ratio	0	0
Commercial Loan [Member] | 65% - 80% | Originated in Fiscal Year Before Latest Fiscal Year
Schedule of Investments [Line Items]
Avg. Debt-Service Coverage Ratio	0	2.13
Commercial Loan [Member] | 65% - 80% | Originated Two Years Before Latest Fiscal Year
Schedule of Investments [Line Items]
Avg. Debt-Service Coverage Ratio	2.20	2.42
Commercial Loan [Member] | 65% - 80% | Originated Three Years Before Latest Fiscal Year
Schedule of Investments [Line Items]
Avg. Debt-Service Coverage Ratio	2.35	3.47
Commercial Loan [Member] | 65% - 80% | Originated Four Years Before Latest Fiscal Year
Schedule of Investments [Line Items]
Avg. Debt-Service Coverage Ratio	3.48	1.77
Commercial Loan [Member] | 65% - 80% | Originated Five or More Years Before Latest Fiscal Year
Schedule of Investments [Line Items]
Avg. Debt-Service Coverage Ratio	1.77	1.77
Commercial Loan [Member] | Less than 65%
Schedule of Investments [Line Items]
Avg. Debt-Service Coverage Ratio	2.73	2.72
Commercial Loan [Member] | Less than 65% | Originated in Current Fiscal Year
Schedule of Investments [Line Items]
Avg. Debt-Service Coverage Ratio	1.62	1.47
Commercial Loan [Member] | Less than 65% | Originated in Fiscal Year Before Latest Fiscal Year
Schedule of Investments [Line Items]
Avg. Debt-Service Coverage Ratio	1.45	2.75
Commercial Loan [Member] | Less than 65% | Originated Two Years Before Latest Fiscal Year
Schedule of Investments [Line Items]
Avg. Debt-Service Coverage Ratio	2.77	2.99
Commercial Loan [Member] | Less than 65% | Originated Three Years Before Latest Fiscal Year
Schedule of Investments [Line Items]
Avg. Debt-Service Coverage Ratio	3.13	2.92
Commercial Loan [Member] | Less than 65% | Originated Four Years Before Latest Fiscal Year
Schedule of Investments [Line Items]
Avg. Debt-Service Coverage Ratio	2.91	2.90
Commercial Loan [Member] | Less than 65% | Originated Five or More Years Before Latest Fiscal Year
Schedule of Investments [Line Items]
Avg. Debt-Service Coverage Ratio	2.78	2.67
Amortized Cost [Member] | Commercial Loan [Member]
Schedule of Investments [Line Items]
Mortgage loans originated in current year	$ 98	$ 400
Mortgage loans originated in year before latest fiscal year	434	929
Mortgage loans originated two years before latest fiscal year	940	1,600
Mortgage loans originated three years before latest fiscal year	1,589	622
Mortgage loans originated four years before latest fiscal year	621	777
Mortgage loans originated five or more years before latest fiscal year	2,563	1,810
Financing Receivable, before Allowance for Credit Loss	6,245	6,138
Amortized Cost [Member] | Commercial Loan [Member] | LTV Greater than 80 Percent
Schedule of Investments [Line Items]
Mortgage loans originated in current year	0	0
Mortgage loans originated in year before latest fiscal year	0	16
Mortgage loans originated two years before latest fiscal year	16	38
Mortgage loans originated three years before latest fiscal year	38	0
Mortgage loans originated four years before latest fiscal year	0	0
Mortgage loans originated five or more years before latest fiscal year	104	105
Financing Receivable, before Allowance for Credit Loss	158	159
Amortized Cost [Member] | Commercial Loan [Member] | 65% - 80%
Schedule of Investments [Line Items]
Mortgage loans originated in current year	0	0
Mortgage loans originated in year before latest fiscal year	0	189
Mortgage loans originated two years before latest fiscal year	189	457
Mortgage loans originated three years before latest fiscal year	489	95
Mortgage loans originated four years before latest fiscal year	94	98
Mortgage loans originated five or more years before latest fiscal year	349	252
Financing Receivable, before Allowance for Credit Loss	1,121	1,091
Amortized Cost [Member] | Commercial Loan [Member] | Less than 65%
Schedule of Investments [Line Items]
Mortgage loans originated in current year	98	400
Mortgage loans originated in year before latest fiscal year	434	724
Mortgage loans originated two years before latest fiscal year	735	1,105
Mortgage loans originated three years before latest fiscal year	1,062	527
Mortgage loans originated four years before latest fiscal year	527	679
Mortgage loans originated five or more years before latest fiscal year	2,110	1,453
Financing Receivable, before Allowance for Credit Loss	$ 4,966	$ 4,888