Investments - Amortized cost, gross unrealized gains and losses and fair value for fixed income securities (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Schedule of Available for Sale Securities
Amortized cost	$ 60,534	$ 56,293
Gross unrealized, Gains	4,229	2,847
Gross unrealized, Losses	(315)	(96)
Fair value	64,448	59,044
U.S. government and agencies
Schedule of Available for Sale Securities
Amortized cost	3,312	4,971
Gross unrealized, Gains	208	141
Gross unrealized, Losses	(1)	(26)
Fair value	3,519	5,086
Municipal
Schedule of Available for Sale Securities
Amortized cost	8,579	8,080
Gross unrealized, Gains	712	551
Gross unrealized, Losses	(6)	(11)
Fair value	9,285	8,620
Corporate
Schedule of Available for Sale Securities
Amortized cost	46,797	41,090
Gross unrealized, Gains	3,227	2,035
Gross unrealized, Losses	(284)	(47)
Fair value	49,740	43,078
Foreign government
Schedule of Available for Sale Securities
Amortized cost	915	968
Gross unrealized, Gains	46	16
Gross unrealized, Losses	0	(5)
Fair value	961	979
ABS
Schedule of Available for Sale Securities
Amortized cost	779	860
Gross unrealized, Gains	4	8
Gross unrealized, Losses	(24)	(6)
Fair value	759	862
MBS
Schedule of Available for Sale Securities
Amortized cost	152	324
Gross unrealized, Gains	32	96
Gross unrealized, Losses	0	(1)
Fair value	$ 184	$ 419

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).

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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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