Investments - Amortized cost, gross unrealized gains and losses and fair value for fixed income securities (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Schedule of Available for Sale Securities
Amortized cost	$ 56,293	$ 57,134
Gross unrealized gains	2,847	993
Gross unrealized losses	(96)	(957)
Fixed income securities	59,044	57,170
U.S. government and agencies
Schedule of Available for Sale Securities
Amortized cost	4,971	5,386
Gross unrealized gains	141	137
Gross unrealized losses	(26)	(6)
Fixed income securities	5,086	5,517
Municipal
Schedule of Available for Sale Securities
Amortized cost	8,080	8,963
Gross unrealized gains	551	249
Gross unrealized losses	(11)	(43)
Fixed income securities	8,620	9,169
Corporate
Schedule of Available for Sale Securities
Amortized cost	41,090	40,557
Gross unrealized gains	2,035	491
Gross unrealized losses	(47)	(890)
Fixed income securities	43,078	40,158
Foreign government
Schedule of Available for Sale Securities
Amortized cost	968	739
Gross unrealized gains	16	13
Gross unrealized losses	(5)	(5)
Fixed income securities	979	747
ABS
Schedule of Available for Sale Securities
Amortized cost	860	1,049
Gross unrealized gains	8	6
Gross unrealized losses	(6)	(10)
Fixed income securities	862	1,045
MBS
Schedule of Available for Sale Securities
Amortized cost	324	440
Gross unrealized gains	96	97
Gross unrealized losses	(1)	(3)
Fixed income securities	$ 419	$ 534

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on 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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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on 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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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

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Amount 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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