Amount of allowance for credit loss for debt security measured at amortized cost (held-to-maturity).

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Amount of increase (decrease) in allowance for credit loss on investment in debt security measured at amortized cost (held-to-maturity).

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-Publisher FASB
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Amount of increase in allowance for credit loss on investment in debt security measured at amortized cost (held-to-maturity), from recovery.

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Investments Investments (Rollforward of expected credit losses HTM) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020	Jun. 30, 2020	Jan. 01, 2020	Dec. 31, 2019
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Debt Securities, Held-to-maturity, Allowance for Credit Loss	$ 45	$ 45	$ 51		$ 0
Debt Securities, Held-to-maturity, Allowance for Credit Loss, Period Increase (Decrease)	2	9
Debt Securities, Held-to-maturity, Allowance for Credit Loss, Recovery	$ (8)	$ (8)
Accounting Standards Update 2016-13 [Member]
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Debt Securities, Held-to-maturity, Allowance for Credit Loss				$ 44