Use of Special Purpose Entities (SPE) and Variable Interest Entities (VIE) - Narrative (Details) $ in Thousands		1 Months Ended	12 Months Ended
	May 16, 2016	Oct. 31, 2016 USD ($)	Dec. 31, 2016 USD ($) securitization	Dec. 31, 2015 USD ($) securitization	Dec. 31, 2014 USD ($)	Dec. 31, 2006 securitization
Variable Interest Entity [Line Items]
Repayments of secured debt | $			$ 126,018	$ 116,136	$ 75,796
Unconsolidated VIE, maximum loss exposure | $			$ 185,300	$ 170,700
Residential Mortgage Loan Securitization
Variable Interest Entity [Line Items]
Number of securitizations completed to date			4
Distressed residential mortgage loans
Variable Interest Entity [Line Items]
Number of securitizations, accounted for as permanent financing			3
K-Series | Consolidated K-Series
Variable Interest Entity [Line Items]
Number of securitizations			5	5		4
K-Series | Non-Financing VIEs, Multi-Family CMBS
Variable Interest Entity [Line Items]
Number of securitizations considered non-financing VIEs			4	1
K-Series | Multi-Family Collateralized Mortgage Backed Securities
Variable Interest Entity [Line Items]
Number of securitizations			2
RBDHC
Variable Interest Entity [Line Items]
Equity method investment, cumulative percentage ownership after all transactions	100.00%
RBDHC | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Variable interest entity, ownership percentage	50.00%
Collateralized Loan Obligation
Variable Interest Entity [Line Items]
Repayments of secured debt | $		$ 55,900	$ 136,314	$ 85,966	$ 83,839