Investments - Amortized cost, gross unrealized gains and losses and fair value for fixed income securities (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Schedule of Available for Sale Securities
Amortized cost	$ 58,945	$ 56,293
Gross unrealized, Gains	2,196	2,847
Gross unrealized, Losses	(1,284)	(96)
Fair value	59,857	59,044
U.S. government and agencies
Schedule of Available for Sale Securities
Amortized cost	5,104	4,971
Gross unrealized, Gains	295	141
Gross unrealized, Losses	0	(26)
Fair value	5,399	5,086
Municipal
Schedule of Available for Sale Securities
Amortized cost	8,182	8,080
Gross unrealized, Gains	555	551
Gross unrealized, Losses	(28)	(11)
Fair value	8,709	8,620
Corporate
Schedule of Available for Sale Securities
Amortized cost	43,624	41,090
Gross unrealized, Gains	1,242	2,035
Gross unrealized, Losses	(1,231)	(47)
Fair value	43,635	43,078
Foreign government
Schedule of Available for Sale Securities
Amortized cost	884	968
Gross unrealized, Gains	30	16
Gross unrealized, Losses	(3)	(5)
Fair value	911	979
ABS
Schedule of Available for Sale Securities
Amortized cost	852	860
Gross unrealized, Gains	3	8
Gross unrealized, Losses	(19)	(6)
Fair value	836	862
MBS
Schedule of Available for Sale Securities
Amortized cost	299	324
Gross unrealized, Gains	71	96
Gross unrealized, Losses	(3)	(1)
Fair value	$ 367	$ 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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-Name Accounting Standards Codification
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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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