Mortgage Loans Held for Sale and Investment - Mortgage Loans Held For Investment - UPB, Fair Value (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2019	Dec. 31, 2018
Mortgage Loans Held For Investment [Roll Forward]
Balance - beginning of period	$ 119
Changes in fair value	1
Balance - end of period	118
Mortgage loans held for investment, net
Accounts, Notes, Loans and Financing Receivable [Line Items]
UPB	25	$ 27
Fair Value	11	$ 13
Mortgage Loans Held For Investment [Roll Forward]
Balance - beginning of period	119
Payments received from borrowers	(2)
Changes in fair value	1
Balance - end of period	$ 118

Mortgage Loans Held For Investment, Change In Fair Value

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- Definition

Mortgage Loans Held For Investment, Nonaccrual Basis, Fair Value

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- Definition

Mortgage Loans Held For Investment, Nonaccrual Basis, Unpaid Principal Balance

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- Definition

Mortgage Loans Held For Investment [Roll Forward]

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- Definition

Mortgage loans held for investment, subject to nonrecourse debt - Legacy Assets, net of allowance for loan losses, respectively

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- Definition

Proceeds From Collection Of Mortgage Loans Held For Investment

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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