Investments (Past Due and Interest Accrual Status of Mortgage Loans) (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Nonaccrual [Line Items]
Mortgage Loans, Gross	$ 83,394	$ 84,344
Greater than 90 Days Past Due and Still Accruing	18	91
Financing Receivable, Nonaccrual	914	1,117
Financing Receivables, Past Due Member
Financing Receivable, Nonaccrual [Line Items]
Mortgage Loans, Gross	758	818
Commercial Mortgage Loans
Financing Receivable, Nonaccrual [Line Items]
Mortgage Loans, Gross	52,300	52,434
Greater than 90 Days Past Due and Still Accruing	0	7
Financing Receivable, Nonaccrual	136	317	$ 176
Commercial Mortgage Loans | Financing Receivables, Past Due Member
Financing Receivable, Nonaccrual [Line Items]
Mortgage Loans, Gross	0	10
Residential Mortgage Loans
Financing Receivable, Nonaccrual [Line Items]
Mortgage Loans, Gross	13,043	13,782
Greater than 90 Days Past Due and Still Accruing	13	64
Financing Receivable, Nonaccrual	519	534	418
Residential Mortgage Loans | Financing Receivables, Past Due Member
Financing Receivable, Nonaccrual [Line Items]
Mortgage Loans, Gross	529	556
Agricultural Mortgage Loans
Financing Receivable, Nonaccrual [Line Items]
Mortgage Loans, Gross	18,051	18,128
Greater than 90 Days Past Due and Still Accruing	5	20
Financing Receivable, Nonaccrual	259	266	$ 137
Agricultural Mortgage Loans | Financing Receivables, Past Due Member
Financing Receivable, Nonaccrual [Line Items]
Mortgage Loans, Gross	$ 229	$ 252