Expected Loss to be Paid Expected Loss to be Paid - Net Economic Loss Development (Benefit) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Schedule of Expected Losses to be Paid [Line Items]
Economic loss development after recoveries for R&W	$ 34	$ (37)	$ 31	$ (39)
RMBS [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Economic loss development after recoveries for R&W	1	(118)	(62)	(183)
RMBS [Member] | United States [Member] | First Lien [Member]
Schedule of Expected Losses to be Paid [Line Items]
Economic loss development after recoveries for R&W	(4)	19	55	50
RMBS [Member] | United States [Member] | Second Lien [Member]
Schedule of Expected Losses to be Paid [Line Items]
Economic loss development after recoveries for R&W	$ 3	$ 99	$ 7	$ 133