Investments - Summary of the Credit Risk Profile of the Commercial Mortgage Loan Portfolio (Details) - Real Estate Loan - Commercial Portfolio Segment $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)
Schedule of Investments [Line Items]
Allowance for credit losses	$ (9)
Allowance for credit losses	$ 1,979	$ 1,947
Weighted Average
Schedule of Investments [Line Items]
Average Debt Service Coverage Ratio	2.01	2.09
Average Loan-to-Value Ratio	60.00%	58.00%
Below 60%
Schedule of Investments [Line Items]
Carrying Value	$ 861	$ 1,136
Below 60% | Weighted Average
Schedule of Investments [Line Items]
Average Debt Service Coverage Ratio	2.20	2.19
60% to 79%
Schedule of Investments [Line Items]
Carrying Value	$ 985	$ 723
60% to 79% | Weighted Average
Schedule of Investments [Line Items]
Average Debt Service Coverage Ratio	1.93	1.98
80% to 100%
Schedule of Investments [Line Items]
Carrying Value	$ 142	$ 88
80% to 100% | Weighted Average
Schedule of Investments [Line Items]
Average Debt Service Coverage Ratio	1.33	1.62