Investments - Debt Securities by Maturity (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Amortized Cost
Less than one year	$ 1,168
One year through five years	7,095
After five years through ten years	4,418
Greater than ten years	4,050
Amortized Cost	20,938	$ 19,396
Fair Value
Less than one year	1,183
One year through five years	7,397
After five years through ten years	4,682
Greater than ten years	4,777
Total	22,346	21,188
Residential mortgage-backed securities
Amortized Cost
Debt securities, maturity, without single maturity date	812
Amortized Cost	812	673
Fair Value
Debt securities, maturity, without single maturity date	829
Total	829	705
Commercial mortgage-backed securities
Amortized Cost
Debt securities, maturity, without single maturity date	1,023
Amortized Cost	1,023	962
Fair Value
Debt securities, maturity, without single maturity date	1,081
Total	1,081	1,046
Other asset-backed securities
Amortized Cost
Debt securities, maturity, without single maturity date	2,372
Amortized Cost	2,372	2,369
Fair Value
Debt securities, maturity, without single maturity date	2,397
Total	$ 2,397	$ 2,403

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