Expected Loss to be Paid Expected Loss to be Paid - Net Economic Loss Development (Benefit) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Schedule of Expected Losses to be Paid [Line Items]
Economic loss development after recoveries for R&W	$ 25	$ 0	$ (14)	$ (5)
RMBS [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Economic loss development after recoveries for R&W	(40)	(40)	(223)	(52)
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	27	13	77	(4)
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	$ 13	$ 27	$ 146	$ 56