Use of Special Purpose Entities and Variable Interest Entities - Narrative (Details) $ in Thousands		1 Months Ended	3 Months Ended
		Feb. 28, 2015 USD ($) securitization	Mar. 31, 2016 USD ($) securitization property		Feb. 29, 2016 USD ($)	Dec. 31, 2015 USD ($) securitization		Dec. 26, 2015 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)
Variable Interest Entity [Line Items]
Securitized debt | $			$ 83,471			$ 116,541			$ 138,300	$ 38,700
Unconsolidated VIE, maximum loss exposure | $			$ 169,600			170,700
Minimum
Variable Interest Entity [Line Items]
Repurchase agreements, expiration period			12 months
Maximum
Variable Interest Entity [Line Items]
Repurchase agreements, expiration period			15 months
PO Security
Variable Interest Entity [Line Items]
Proceeds from sale of investment | $		$ 44,300
Gain on sale of investment | $		$ 1,500
Multi-Family Collateralized Mortgage Backed Securities
Variable Interest Entity [Line Items]
Securitized debt | $	[1],[3]		$ 27,781	[2]		27,613	[4]
Collateralized Recourse Financing
Variable Interest Entity [Line Items]
Securitized debt | $	[1],[5]		$ 55,690	[6]		55,629	[7]
Repurchase agreements, expiration period			3 years
Distressed Residential Mortgage Loan Securitization
Variable Interest Entity [Line Items]
Number of securitizations | securitization			4
Securitized debt | $	[1],[9]		$ 0	[8]		$ 33,299	[10]
Number of securitizations with no principal payments | securitization			2
Distressed Residential Mortgage Loan Securitization | Minimum
Variable Interest Entity [Line Items]
Number of real estate properties | property			1
Securitization, revolving period			1 year
Distressed Residential Mortgage Loan Securitization | Maximum
Variable Interest Entity [Line Items]
Number of real estate properties | property			4
Securitization, revolving period			2 years
Residential mortgage loans held in securitization trusts
Variable Interest Entity [Line Items]
Number of securitizations completed to date | securitization			4
Number of securitizations, consolidated, accounted for as permanent financing | securitization			3
K-Series | Consolidated K-Series
Variable Interest Entity [Line Items]
Number of securitizations | securitization			5			5
K-Series | Multi-Family Collateralized Mortgage Backed Securities
Variable Interest Entity [Line Items]
Number of securitizations | securitization			2			2
Number of consolidated securitizations | securitization			1			1
K-Series | Collateralized Recourse Financing
Variable Interest Entity [Line Items]
Number of securitizations | securitization			3			3
K-Series | Non-Financings, Multi-Family CMBS
Variable Interest Entity [Line Items]
Number of securitizations | securitization		1
Number of securitizations, non-financing VIE's | securitization			1			1
Multi-family collateralized debt obligations
Variable Interest Entity [Line Items]
Transfer of financial assets, amount derecognized | $		$ 1,000,000
Multi-Family Collateralized Mortgage Backed Securities
Variable Interest Entity [Line Items]
Transfer of financial assets, amount derecognized | $		$ 1,100,000
Distressed residential mortgage loans held in securitization trust, (net)
Variable Interest Entity [Line Items]
Residential mortgage loans held in securitization trusts (net), carrying value | $					$ 31,900	$ 114,214	[10]	$ 5,500

[1] Classified as securitized debt in the liability section of the Company’s accompanying condensed consolidated balance sheets, net of debt issuance costs.

[2] The Company classified the multi-family CMBS issued by two K-Series securitizations and held by this Financing VIE as available for sale securities as the purpose is not to trade these securities. The Financing VIE consolidated one K-Series securitization that issued certain of the multi-family CMBS owned by the Company, including its assets, liabilities, income and expenses, in its financial statements, as based on a number of factors, the Company determined that it was the primary beneficiary and has a controlling financial interest in this particular K-Series securitization (see Note 6).

[3] The Company engaged in the re-securitization transaction primarily for the purpose of obtaining non-recourse financing on a portion of its multi-family CMBS portfolio. As a result of engaging in this transaction, the Company remains economically exposed to the first loss position on the underlying multi-family CMBS transferred to the Consolidated VIE. The holders of the Note have no recourse to the general credit of the Company, but the Company does have the obligation, under certain circumstances, to repurchase assets upon the breach of certain representations and warranties. The Company will receive all remaining cash flow, if any, through its retained ownership.

[4] The Company classified the multi-family CMBS issued by two K-Series securitizations and held by this Financing VIE as available for sale securities as the purpose is not to trade these securities. The Financing VIE consolidated one K-Series securitization that issued certain of the multi-family CMBS owned by the Company, including its assets, liabilities, income and expenses, in its financial statements, as based on a number of factors, the Company determined that it was the primary beneficiary and has a controlling financial interest in this particular K-Series securitization (see Note 6).

[5] The Company entered into a CMBS Master Repurchase Agreement with a three-year term for the purpose of financing a portion of its multi-family CMBS portfolio. In connection with the transaction, the Company agreed to guarantee the due and punctual payment of its wholly-owned subsidiary's obligations under the CMBS Master Repurchase Agreement.

[6] The multi-family CMBS serving as collateral under the November 2013 collateralized recourse financing are comprised of securities issued from three separate Freddie Mac-sponsored multi-family K-Series securitizations. The Financing VIE consolidated these K-Series securitizations, including their assets, liabilities, income and expenses, in its financial statements as based on a number of factors, the Company determined that it was the primary beneficiary and has a controlling financial interest in such K-Series securitizations (see Note 6). One of the Company’s Freddie Mac-sponsored multi-family K-Series securitizations included in the Consolidated K-Series is not subject to any financing as of March 31, 2016.

[7] The multi-family CMBS serving as collateral under the November 2013 collateralized recourse financing are comprised of securities issued from three separate Freddie Mac-sponsored multi-family K-Series securitizations. The Financing VIE consolidated these K-Series securitizations, including their assets, liabilities, income and expenses, in its financial statements as based on a number of factors, the Company determined that it was the primary beneficiary and has a controlling financial interest in such K-Series securitizations (see Note 6).

[8] In February 2016, the Company repaid the Company’s outstanding notes from its distressed residential mortgage loan securitizations transactions completed in 2013 with original principal amounts of $138.3 million and outstanding principal balance at the time of repayment amounting to $31.9 million. With the repayment of the notes, the Company terminated and deconsolidated the Financing VIEs that facilitated these financing transactions and the distressed residential loans serving as collateral on the notes were transferred back to the Company.

[9] The Company engaged in these transactions for the purpose of financing distressed residential mortgage loans acquired by the Company. The distressed residential mortgage loans serving as collateral for the financings are comprised of performing, re-performing and, to a lesser extent, non-performing, fixed and adjustable-rate, fully-amortizing, interest only and balloon, seasoned mortgage loans secured by first liens on one to four family properties. Two of the four securitization transactions provide for a revolving period of one to two years from the date of the respective financing (“Revolving Period”) where no principal payments will be made on these two notes. All cash proceeds generated by the distressed residential mortgage loans and received by the respective securitization trust during the Revolving Period, after payment of interest on the respective note, reserve amounts and certain other transaction expenses, will be available for the purchase by the respective trust of additional mortgage loans that satisfy certain eligibility criteria. In December 2015, the Company repaid the Company’s outstanding notes from its distressed residential mortgage loan securitization transaction completed in December 2012 with an original principal amount of $38.7 million and outstanding principal balance at the time of repayment amounting to $5.5 million. With the repayment of the notes, the Company terminated and deconsolidated the Financing VIE that facilitated this financing transaction and the distressed residential loans serving as collateral on the notes were transferred back to the Company.

[10] In December 2015, the Company repaid the Company’s outstanding notes from its distressed residential mortgage loan securitization transaction completed in December 2012 with an original principal amount of $38.7 million and outstanding principal balance at the time of repayment amounting to $5.5 million. With the repayment of the notes, the Company terminated and deconsolidated the Financing VIE that facilitated this financing transaction and the distressed residential loans serving as collateral on the notes were transferred back to the Company.