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Investments Investments (Rollforward of expected credit-losses, AFS) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Mar. 31, 2020	Jan. 01, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]
Debt Securities, Available-for-sale, Allowance for Credit Loss	$ 69		$ 69		$ 176		$ 0
Debt Securities, Available-for-sale, Allowance for Credit Loss, Purchased with Credit Deterioration, Increase	3		5
Debt Securities, Available-for-sale, Allowance for Credit Loss, Period Increase (Decrease)	29		178
Debt Securities, Available-for-sale, Allowance for Credit Loss, Recovery	(134)		(134)
Debt Securities, Available-for-sale, Allowance for Credit Loss, Writeoff	(5)		(5)
Accounting Standards Update 2016-13 [Member]
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]
Debt Securities, Available-for-sale, Allowance for Credit Loss						$ 25
Debt Securities, Available-for-sale, Allowance for Credit Loss, Period Increase (Decrease)	$ 104	$ 0	$ (46)	$ 0