Guarantees Repurchased Mortgage Loan (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Repurchased mortgage loans, carrying value	$ 193	$ 199
Performing Financial Instruments [Member] | Loans Held-For-Investment [Member]
Repurchased mortgage loans, carrying value	181	183
Nonperforming Financing Receivable [Member] | Loans Held-For-Investment [Member]
Repurchased mortgage loans, carrying value	$ 12	$ 16