Expected Loss to be Paid - Narrative Net Expected Recoveries from Breaches of R&W (Details) - RMBS [Member] - United States [Member] - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Schedule of Expected Losses to be Paid [Line Items]
Future net R&W benefit	$ 34	$ 5
Second Lien [Member]
Schedule of Expected Losses to be Paid [Line Items]
Guarantor Obligations, Projected Loss Assumptions, Period to Reach Intermediate Conditional Default Rate	28 months
Second Lien [Member] | Most Stressful [Member]
Schedule of Expected Losses to be Paid [Line Items]
Guarantor Obligations, Projected Loss Assumptions, Period to Reach Intermediate Conditional Default Rate	31 months