Investments - Debt Securities by Maturity (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Amortized Cost
Less than one year	$ 1,028
One year through five years	5,507
After five years through ten years	3,081
Greater than ten years	3,723
Amortized Cost	15,898	$ 15,119
Fair Value
Less than one year	1,034
One year through five years	5,702
After five years through ten years	3,296
Greater than ten years	4,252
Total	16,922	15,255
Residential mortgage-backed securities
Amortized Cost
Debt securities, maturity, without single maturity date	508
Amortized Cost	508	567
Fair Value
Debt securities, maturity, without single maturity date	533
Total	533	577
Commercial mortgage-backed securities
Amortized Cost
Debt securities, maturity, without single maturity date	654
Amortized Cost	654	594
Fair Value
Debt securities, maturity, without single maturity date	700
Total	700	605
Other asset-backed securities
Amortized Cost
Debt securities, maturity, without single maturity date	1,397
Amortized Cost	1,397	1,097
Fair Value
Debt securities, maturity, without single maturity date	1,405
Total	$ 1,405	$ 1,085

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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