Investments - Allowance for Credit Losses (Details) $ in Millions	1 Months Ended	6 Months Ended
	Jun. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Provision for loan losses	$ 21
For initial credit losses on purchased loans accounted for as PCD financial assets	7
Ending Balance	28	$ 28
Financing Receivable, Recorded Investment, Aging [Abstract]
Total loans that are 90 days past due and still accruing	20	20
Debt Securities, Available-for-sale, Purchased with Credit Deterioration, Amount at Purchase Price [Abstract]
Purchase price		265
Allowance for credit losses at acquisition		35
Discount (or premiums) attributable to other factors		84
AFS purchased credit-deteriorated par value		384
Residential Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Provision for loan losses	19
For initial credit losses on purchased loans accounted for as PCD financial assets	7
Ending Balance	26	26
Financing Receivable, Recorded Investment, Aging [Abstract]
Total loans that are 90 days past due and still accruing	20	20
Commercial Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Provision for loan losses	2
For initial credit losses on purchased loans accounted for as PCD financial assets	0
Ending Balance	2	2
Financing Receivable, Recorded Investment, Aging [Abstract]
Total loans that are 90 days past due and still accruing	$ 0	$ 0