Mortgage Loans (Policies)	6 Months Ended
Mortgage Loans (Policies)	Jun. 30, 2019
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Abstract]
Finance, Loan and Lease Receivables, Held-for-investment, Policy [Policy Text Block]	We define the recorded investment of HFI loans as unpaid principal balance, net of unamortized premiums and discounts, other cost basis adjustments, and accrued interest receivable.We report the carrying value of HFI loans at the unpaid principal balance, net of unamortized premiums and discounts, other cost basis adjustments, and an allowance for loan losses.
Finance, Loan and Lease Receivables, Held-for-sale, Policy [Policy Text Block]	We report the carrying value of HFS loans at the lower of cost or fair value and record valuation changes in “Investment gains, net” in our condensed consolidated statements of operations and comprehensive income.
Nonaccrual Loans [Policy Text Block]	We discontinue accruing interest on loans when we believe collectibility of principal or interest is not reasonably assured, which for a single-family loan we have determined, based on our historical experience, to be when the loan becomes two months or more past due according to its contractual terms. Interest previously accrued but not collected is reversed through interest income at the date a loan is placed on nonaccrual status. We return a non-modified single-family loan to accrual status at the point that the borrower brings the loan current. We return a modified single-family loan to accrual status at the point that the borrower successfully makes all required payments during the trial period (generally three to four months) and the modification is made permanent. We place a multifamily loan on nonaccrual status when the loan becomes three months or more past due according to its contractual terms or is deemed to be individually impaired, unless the loan is well secured such that collectibility of principal and accrued interest is reasonably assured. We return a multifamily loan to accrual status when the borrower cures the delinquency of the loan or we otherwise determine that the loan is well secured such that collectibility is reasonably assured.
Troubled Debt Restructurings [Policy Text Block]	A modification to the contractual terms of a loan that results in granting a concession to a borrower experiencing financial difficulties is considered a TDR.

Disclosure of accounting policy for those finance, loan and lease receivables classified as held for investment. This disclosure may include (1) the basis at which such receivables are carried in the entity's statements of financial position (2) how the level of the allowance for loan and lease losses is determined (3) when impairments, charge-offs or recoveries are recognized for such receivables (4) the treatment of commitment and other fees and loan origination costs (including, if applicable, how the entity accounts for fees and costs associated with credit cards that are either purchased or originated) (5) the treatment of any premiums or discounts or unearned income (6) the entity's income recognition policies for such receivables, including those that are impaired, past due or placed on nonaccrual status (for impaired loans, the policy for recognizing interest income on such loans, including how cash receipts are recorded) and (7) the treatment of foreclosures or repossessions.

- Definition

Disclosure of accounting policy for those finance, loan and lease receivables classified as held for sale. This disclosure may include how the entity determines when to classify a loan or receivable as held for sale, the basis at which such receivables are carried in the entity's statements of financial position, how such receivables are valued, the method used to determine the lower of cost or fair value (that is, on an aggregate or individual asset basis), the treatment of commitment and other fees and origination costs, and how transfers to and from the held for investment portfolio are accounted for.

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