Investments - Mortgage Loans, Net by Property Type and Geographic Region (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Loans and Leases Receivable Disclosure [Line Items]
Mortgage loans, net of allowances	$ 18,209	$ 15,938
Commercial mortgage loans
Loans and Leases Receivable Disclosure [Line Items]
Mortgage loans, net of allowances	$ 13,387	$ 11,448
Commercial mortgage loans | Property Type Concentration Risk | Mortgage Loans, Net
Loans and Leases Receivable Disclosure [Line Items]
Percentage concentration risk	100.00%	100.00%
Commercial mortgage loans | Geographic Concentration Risk | Mortgage Loans, Net
Loans and Leases Receivable Disclosure [Line Items]
Percentage concentration risk	100.00%	100.00%
Commercial mortgage loans | Total U.S. Region
Loans and Leases Receivable Disclosure [Line Items]
Mortgage loans, net of allowances	$ 11,705	$ 10,821
Commercial mortgage loans | Total U.S. Region | Geographic Concentration Risk | Mortgage Loans, Net
Loans and Leases Receivable Disclosure [Line Items]
Percentage concentration risk	87.40%	94.50%
Commercial mortgage loans | East North Central
Loans and Leases Receivable Disclosure [Line Items]
Mortgage loans, net of allowances	$ 1,360	$ 1,209
Commercial mortgage loans | East North Central | Geographic Concentration Risk | Mortgage Loans, Net
Loans and Leases Receivable Disclosure [Line Items]
Percentage concentration risk	10.20%	10.50%
Commercial mortgage loans | East South Central
Loans and Leases Receivable Disclosure [Line Items]
Mortgage loans, net of allowances	$ 422	$ 402
Commercial mortgage loans | East South Central | Geographic Concentration Risk | Mortgage Loans, Net
Loans and Leases Receivable Disclosure [Line Items]
Percentage concentration risk	3.20%	3.50%
Commercial mortgage loans | Middle Atlantic
Loans and Leases Receivable Disclosure [Line Items]
Mortgage loans, net of allowances	$ 3,222	$ 3,069
Commercial mortgage loans | Middle Atlantic | Geographic Concentration Risk | Mortgage Loans, Net
Loans and Leases Receivable Disclosure [Line Items]
Percentage concentration risk	24.10%	26.80%
Commercial mortgage loans | Mountain
Loans and Leases Receivable Disclosure [Line Items]
Mortgage loans, net of allowances	$ 465	$ 487
Commercial mortgage loans | Mountain | Geographic Concentration Risk | Mortgage Loans, Net
Loans and Leases Receivable Disclosure [Line Items]
Percentage concentration risk	3.50%	4.20%
Commercial mortgage loans | New England
Loans and Leases Receivable Disclosure [Line Items]
Mortgage loans, net of allowances	$ 366	$ 350
Commercial mortgage loans | New England | Geographic Concentration Risk | Mortgage Loans, Net
Loans and Leases Receivable Disclosure [Line Items]
Percentage concentration risk	2.70%	3.10%
Commercial mortgage loans | Pacific
Loans and Leases Receivable Disclosure [Line Items]
Mortgage loans, net of allowances	$ 3,129	$ 2,746
Commercial mortgage loans | Pacific | Geographic Concentration Risk | Mortgage Loans, Net
Loans and Leases Receivable Disclosure [Line Items]
Percentage concentration risk	23.30%	24.00%
Commercial mortgage loans | South Atlantic
Loans and Leases Receivable Disclosure [Line Items]
Mortgage loans, net of allowances	$ 1,957	$ 1,773
Commercial mortgage loans | South Atlantic | Geographic Concentration Risk | Mortgage Loans, Net
Loans and Leases Receivable Disclosure [Line Items]
Percentage concentration risk	14.50%	15.50%
Commercial mortgage loans | West North Central
Loans and Leases Receivable Disclosure [Line Items]
Mortgage loans, net of allowances	$ 128	$ 145
Commercial mortgage loans | West North Central | Geographic Concentration Risk | Mortgage Loans, Net
Loans and Leases Receivable Disclosure [Line Items]
Percentage concentration risk	1.00%	1.30%
Commercial mortgage loans | West South Central
Loans and Leases Receivable Disclosure [Line Items]
Mortgage loans, net of allowances	$ 656	$ 640
Commercial mortgage loans | West South Central | Geographic Concentration Risk | Mortgage Loans, Net
Loans and Leases Receivable Disclosure [Line Items]
Percentage concentration risk	4.90%	5.60%
Commercial mortgage loans | UNITED KINGDOM
Loans and Leases Receivable Disclosure [Line Items]
Mortgage loans, net of allowances	$ 827	$ 0
Commercial mortgage loans | UNITED KINGDOM | Geographic Concentration Risk | Mortgage Loans, Net
Loans and Leases Receivable Disclosure [Line Items]
Percentage concentration risk	6.20%	0.00%
Commercial mortgage loans | Other
Loans and Leases Receivable Disclosure [Line Items]
Mortgage loans, net of allowances	$ 855	$ 627
Commercial mortgage loans | Other | Geographic Concentration Risk | Mortgage Loans, Net
Loans and Leases Receivable Disclosure [Line Items]
Percentage concentration risk	6.40%	5.50%
Commercial mortgage loans | International
Loans and Leases Receivable Disclosure [Line Items]
Mortgage loans, net of allowances	$ 1,682	$ 627
Commercial mortgage loans | International | Geographic Concentration Risk | Mortgage Loans, Net
Loans and Leases Receivable Disclosure [Line Items]
Percentage concentration risk	12.60%	5.50%
Commercial mortgage loans | Hotels
Loans and Leases Receivable Disclosure [Line Items]
Mortgage loans, net of allowances	$ 1,392	$ 1,294
Commercial mortgage loans | Hotels | Property Type Concentration Risk | Mortgage Loans, Net
Loans and Leases Receivable Disclosure [Line Items]
Percentage concentration risk	10.40%	11.30%
Commercial mortgage loans | Retail
Loans and Leases Receivable Disclosure [Line Items]
Mortgage loans, net of allowances	$ 2,125	$ 2,083
Commercial mortgage loans | Retail | Property Type Concentration Risk | Mortgage Loans, Net
Loans and Leases Receivable Disclosure [Line Items]
Percentage concentration risk	15.90%	18.20%
Commercial mortgage loans | Office building
Loans and Leases Receivable Disclosure [Line Items]
Mortgage loans, net of allowances	$ 4,125	$ 3,589
Commercial mortgage loans | Office building | Property Type Concentration Risk | Mortgage Loans, Net
Loans and Leases Receivable Disclosure [Line Items]
Percentage concentration risk	30.80%	31.40%
Commercial mortgage loans | Industrial
Loans and Leases Receivable Disclosure [Line Items]
Mortgage loans, net of allowances	$ 1,956	$ 1,362
Commercial mortgage loans | Industrial | Property Type Concentration Risk | Mortgage Loans, Net
Loans and Leases Receivable Disclosure [Line Items]
Percentage concentration risk	14.60%	11.90%
Commercial mortgage loans | Apartment
Loans and Leases Receivable Disclosure [Line Items]
Mortgage loans, net of allowances	$ 2,710	$ 2,441
Commercial mortgage loans | Apartment | Property Type Concentration Risk | Mortgage Loans, Net
Loans and Leases Receivable Disclosure [Line Items]
Percentage concentration risk	20.20%	21.30%
Commercial mortgage loans | Other commercial
Loans and Leases Receivable Disclosure [Line Items]
Mortgage loans, net of allowances	$ 1,079	$ 679
Commercial mortgage loans | Other commercial | Property Type Concentration Risk | Mortgage Loans, Net
Loans and Leases Receivable Disclosure [Line Items]
Percentage concentration risk	8.10%	5.90%