Investments - Debt Securities by Maturity (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Amortized Cost
Less than one year	$ 1,276
One year through five years	6,346
After five years through ten years	3,748
Greater than ten years	4,022
Gross Amortized Cost	19,396	$ 15,898
Fair Value
Less than one year	1,291
One year through five years	6,698
After five years through ten years	4,121
Greater than ten years	4,924
Total	21,188	16,922
Residential mortgage-backed securities
Amortized Cost
Debt securities, maturity, without single maturity date	673
Gross Amortized Cost	673	508
Fair Value
Debt securities, maturity, without single maturity date	705
Total	705	533
Commercial mortgage-backed securities
Amortized Cost
Debt securities, maturity, without single maturity date	962
Gross Amortized Cost	962	654
Fair Value
Debt securities, maturity, without single maturity date	1,046
Total	1,046	700
Other asset-backed securities
Amortized Cost
Debt securities, maturity, without single maturity date	2,369
Gross Amortized Cost	2,369	1,397
Fair Value
Debt securities, maturity, without single maturity date	2,403
Total	$ 2,403	$ 1,405

Debt Securities, Available-For-Sale, Allocated And Single Maturity Date, Maturity, After 10 Years, Amortized Cost, Net

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