Related party transactions (Details 1) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Receivable from servicer	$ 16,067	$ 12,481
Investment in subordinated debt securities	6,303	6,323
Management fee payable	750	750
Gregory | Receivables from Servicer
Related Party Transaction [Line Items]
Receivable from servicer	16,067	12,481
Gregory | Accrued expenses and other liabilities
Related Party Transaction [Line Items]
Servicing fees payable	208	195
Oileus Residential Loan Trust | Investment in securities
Related Party Transaction [Line Items]
Investment in subordinated debt securities	6,303	6,323
Thetis | Management fee payable
Related Party Transaction [Line Items]
Management fee payable	$ 750	$ 750