Investments, Amortized Cost Basis of Mortgage Loans for Each Credit Quality Indicator by Year of Origination (Details) $ in Millions	6 Months Ended
	Jun. 30, 2020 USD ($)
Mortgage Loans [Abstract]
Loans placed in nonaccrual status	$ 0
Interest income write-off	0
Less than 90 Days Past Due [Member]
Mortgage Loans [Abstract]
Loans past due	22
Mortgage Loans [Member]
Mortgage Loans Amortized Cost Basis by Origination Year [Abstract]
2020	79	[1]
2019	297	[1]
2018	115	[1]
2017	223	[1]
2016	85	[1]
Prior	263	[1]
Total	1,062	[1]
Mortgage Loans [Member] | DSCR Greater than or Equal to 1.6x, LTV Less than 55% [Member]
Mortgage Loans Amortized Cost Basis by Origination Year [Abstract]
2020	60	[1]
2019	33	[1]
2018	19	[1]
2017	100	[1]
2016	41	[1]
Prior	129	[1]
Total	382	[1]
Mortgage Loans [Member] | DSCR Greater than or Equal to 1.6x, LTV 55% to 65% [Member]
Mortgage Loans Amortized Cost Basis by Origination Year [Abstract]
2019	32	[1]
2018	29	[1]
2017	41	[1]
2016	4	[1]
Total	106	[1]
Mortgage Loans [Member] | DSCR Greater than or Equal to 1.6x, LTV Greater than 65% [Member]
Mortgage Loans Amortized Cost Basis by Origination Year [Abstract]
2019	5	[1]
Total	5	[1]
Mortgage Loans [Member] | DSCR Between 1.2 to 1.6x, LTV Less than 55% [Member]
Mortgage Loans Amortized Cost Basis by Origination Year [Abstract]
2019	32	[1]
2018	10	[1]
2017	13	[1]
2016	16	[1]
Prior	125	[1]
Total	196	[1]
Mortgage Loans [Member] | DSCR Between 1.2 to 1.6x, LTV 55% to 65% [Member]
Mortgage Loans Amortized Cost Basis by Origination Year [Abstract]
2019	83	[1]
2018	32	[1]
2017	32	[1]
Total	147	[1]
Mortgage Loans [Member] | DSCR Between 1.2 to 1.6x, LTV Greater than 65% [Member]
Mortgage Loans Amortized Cost Basis by Origination Year [Abstract]
2020	19	[1]
2019	74	[1]
Total	93	[1]
Mortgage Loans [Member] | DSCR Less than or Equal to 1.2x, LTV Less than 55% [Member]
Mortgage Loans Amortized Cost Basis by Origination Year [Abstract]
2019	2	[1]
2018	11	[1]
Prior	9	[1]
Total	22	[1]
Mortgage Loans [Member] | DSCR Less than or Equal to 1.2x, LTV 55% to 65% [Member]
Mortgage Loans Amortized Cost Basis by Origination Year [Abstract]
2019	14	[1]
2018	14	[1]
Total	28	[1]
Mortgage Loans [Member] | DSCR Less than or Equal to 1.2x, LTV Greater than 65% [Member]
Mortgage Loans Amortized Cost Basis by Origination Year [Abstract]
2019	22	[1]
2017	37	[1]
2016	24	[1]
Total	$ 83	[1]

[1] The values in the table above reflect DSCR on a standardized amortization period and LTV based on the most recent appraised values trended forward using changes in a commercial real estate price index.