Use of Special Purpose Entities and Variable Interest Entities - Financing VIEs Securitized Debt by Contractual Maturity (Details) $ in Thousands	Jun. 30, 2018 USD ($) securitization	Dec. 31, 2017 USD ($)
Variable Interest Entity [Line Items]
Total	$ 215,580
Carrying value	61,026	$ 81,537
Financing VIE
Variable Interest Entity [Line Items]
Within 24 months	31,827	53,089
Over 24 months to 36 months	0	0
Over 36 months	33,262	33,350
Total	65,089	86,439
Discount	(3,615)	(4,232)
Debt issuance cost	(448)	(670)
Carrying value	$ 61,026	$ 81,537
Residential mortgage loans held In securitization trusts net
Variable Interest Entity [Line Items]
Number of securitizations completed to date \| securitization	4
Number of securitizations, consolidated, accounted for as permanent financing \| securitization	3

Long-term Debt, Maturities, Repayments of Principal in Next Rolling Twenty Four Months

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Number of Securitizations Completed to Date

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Number of Securitizations, Consolidated, Accounted for as Permanent Financing

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The value of the collateral (typically cash) that the entity receives in a financing transaction in exchange for securities lent. This item represents a liability in the financial statements of the lender of the securities.

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Amount, after accumulated amortization, of debt discount.

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Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the fourth rolling twelve months following the latest balance sheet. For interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the third rolling twelve months following the latest balance sheet. For interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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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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