Investments - Mortgage Loans by Region and Property Type (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss		$ 4,215
Financing Receivable, Allowance for Credit Loss		0
Commercial Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 4,531	$ 4,215
Percent of Total	100.00%	100.00%
Financing Receivable, Allowance for Credit Loss	$ 38	$ 0	$ 1	$ 1
Commercial Loan [Member] | Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 1,339	$ 1,167
Percent of Total	29.50%	27.70%
Commercial Loan [Member] | Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 1,498	$ 1,313
Percent of Total	33.10%	31.20%
Commercial Loan [Member] | Office
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 774	$ 723
Percent of Total	17.10%	17.20%
Commercial Loan [Member] | Retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 788	$ 735
Percent of Total	17.40%	17.40%
Commercial Loan [Member] | Residential Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 92	$ 137
Percent of Total	2.00%	3.20%
Commercial Loan [Member] | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 40	$ 140
Percent of Total	0.90%	3.30%
Commercial Loan [Member] | Mortgage loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of Total	100.00%	100.00%
Commercial Loan [Member] | East North Central
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 290	$ 270
Commercial Loan [Member] | East North Central | Mortgage loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of Total	6.40%	6.40%
Commercial Loan [Member] | Middle Atlantic
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 291	$ 319
Commercial Loan [Member] | Middle Atlantic | Mortgage loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of Total	6.40%	7.50%
Commercial Loan [Member] | Mountain
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 254	$ 109
Commercial Loan [Member] | Mountain | Mortgage loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of Total	5.60%	2.60%
Commercial Loan [Member] | New England
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 397	$ 344
Commercial Loan [Member] | New England | Mortgage loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of Total	8.80%	8.20%
Commercial Loan [Member] | Pacific
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 1,001	$ 906
Commercial Loan [Member] | Pacific | Mortgage loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of Total	22.10%	21.50%
Commercial Loan [Member] | South Atlantic
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 1,038	$ 944
Commercial Loan [Member] | South Atlantic | Mortgage loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of Total	22.90%	22.40%
Commercial Loan [Member] | West North Central
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 44	$ 46
Commercial Loan [Member] | West North Central | Mortgage loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of Total	1.00%	1.10%
Commercial Loan [Member] | West South Central
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 433	$ 439
Commercial Loan [Member] | West South Central | Mortgage loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of Total	9.50%	10.40%
Commercial Loan [Member] | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 783	$ 838
Commercial Loan [Member] | Other | Mortgage loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of Total	17.30%	19.90%