Investments - Commercial Mortgage Loan Portfolio (Details) - Real Estate Loan - Commercial Portfolio Segment $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)
Schedule of Investments [Line Items]
Carrying value, after allowance for credit loss, including assets held for sale	$ 1,562	$ 1,533
Weighted Average
Schedule of Investments [Line Items]
Average Debt Service Coverage Ratio, including assets held for sale	1.81	1.82
Average Loan-to-Value Ratio, including assets held for sale	0.64	0.64
Below 60%
Schedule of Investments [Line Items]
Carrying value, after allowance for credit loss, including assets held for sale	$ 810	$ 802
Below 60% | Weighted Average
Schedule of Investments [Line Items]
Average Debt Service Coverage Ratio, including assets held for sale	2.12	2.13
60% to 79%
Schedule of Investments [Line Items]
Carrying value, after allowance for credit loss, including assets held for sale	$ 594	$ 574
60% to 79% | Weighted Average
Schedule of Investments [Line Items]
Average Debt Service Coverage Ratio, including assets held for sale	1.75	1.77
80% to 100%
Schedule of Investments [Line Items]
Carrying value, after allowance for credit loss, including assets held for sale	$ 158	$ 157
80% to 100% | Weighted Average
Schedule of Investments [Line Items]
Average Debt Service Coverage Ratio, including assets held for sale	0.63	0.65