Fair Value of Financial Instruments - Narrative (Details)	12 Months Ended
	Dec. 31, 2015
CMBS | Minimum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value inputs, discount rate	4.50%
CMBS | Maximum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value inputs, discount rate	10.50%
Multi-family loans held in securitization trusts | Minimum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value inputs, discount rate	3.00%
Multi-family loans held in securitization trusts | Maximum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value inputs, discount rate	5.60%