Guarantees Repurchased Mortgage Loan (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Repurchased mortgage loans, carrying value	$ 144	$ 199
Performing Financial Instruments [Member] | Loans Held-For-Investment [Member]
Repurchased mortgage loans, carrying value	135	183
Nonperforming Financing Receivable [Member] | Loans Held-For-Investment [Member]
Repurchased mortgage loans, carrying value	$ 9	$ 16