Consolidated K-Series - Condensed Balance Sheet of Consolidated K-Series (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Assets
Multi-family loans held in securitization trusts, at fair value	$ 6,939,844	$ 7,105,336
Total Assets	8,951,631	9,056,242
Liabilities and Equity
Total liabilities	8,100,469	8,175,716
Equity	848,075	880,526
Total Liabilities and Stockholders' Equity	8,951,631	9,056,242
Consolidated K-Series
Assets
Multi-family loans held in securitization trusts, at fair value	6,939,844	7,105,336
Receivables	24,098	24,579
Total Assets	6,963,942	7,129,915
Liabilities and Equity
Multi-family CDOs	6,624,896	6,818,901
Accrued expenses	24,003	24,483
Total liabilities	6,648,899	6,843,384
Equity	315,043	286,531
Total Liabilities and Stockholders' Equity	$ 6,963,942	$ 7,129,915