Variable interest entities and securitization activities - Securitized Debt Obligations (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Variable interest entities
Current Principal Balance	$ 1,776,888	$ 1,735,493
Current principal balance of non-company sponsored securitized loans	7,200	7,300
Consolidated VIEs
Variable interest entities
Current Principal Balance	1,718,560	1,845,886
Carrying value	$ 1,684,898	$ 1,807,883
Weighted Average Rate	3.60%	3.70%
Waterfall Victoria Mortgage Trust 2011-SBC2
Variable interest entities
Current Principal Balance	$ 6,131	$ 6,399
Carrying value	$ 6,131	$ 6,399
Weighted Average Rate	5.50%	5.50%
ReadyCap Lending Small Business Trust 2019-2
Variable interest entities
Current Principal Balance	$ 117,876	$ 131,032
Carrying value	$ 117,876	$ 129,007
Weighted Average Rate	4.30%	4.30%
Sutherland Commercial Mortgage Trust 2017-SBC6
Variable interest entities
Current Principal Balance	$ 38,679	$ 42,309
Carrying value	$ 37,958	$ 41,486
Weighted Average Rate	3.50%	3.40%
Sutherland Commercial Mortgage Trust 2018-SBC7
Variable interest entities
Current Principal Balance	$ 114,938	$ 138,235
Carrying value	$ 113,166	$ 136,212
Weighted Average Rate	4.70%	4.70%
Sutherland Commercial Mortgage Trust 2019-SBC8
Variable interest entities
Current Principal Balance	$ 210,516	$ 219,617
Carrying value	$ 207,679	$ 216,981
Weighted Average Rate	2.90%	2.90%
ReadyCap Commercial Mortgage Trust 2014-1
Variable interest entities
Current Principal Balance	$ 18,406	$ 18,626
Carrying value	$ 18,411	$ 18,632
Weighted Average Rate	5.80%	5.60%
ReadyCap Commercial Mortgage Trust 2015-2
Variable interest entities
Current Principal Balance	$ 60,344	$ 64,239
Carrying value	$ 57,772	$ 61,443
Weighted Average Rate	4.50%	4.50%
ReadyCap Commercial Mortgage Trust 2016-3
Variable interest entities
Current Principal Balance	$ 27,295	$ 32,269
Carrying value	$ 25,927	$ 30,777
Weighted Average Rate	3.60%	4.70%
ReadyCap Commercial Mortgage Trust 2018-4
Variable interest entities
Current Principal Balance	$ 114,670	$ 121,179
Carrying value	$ 111,058	$ 117,428
Weighted Average Rate	3.90%	3.90%
ReadyCap Commercial Mortgage Trust 2019-5
Variable interest entities
Current Principal Balance	$ 282,994	$ 309,296
Carrying value	$ 273,342	$ 299,273
Weighted Average Rate	4.10%	4.10%
ReadyCap Commercial Mortgage Trust 2019-6
Variable interest entities
Current Principal Balance	$ 378,765	$ 379,400
Carrying value	$ 371,539	$ 371,939
Weighted Average Rate	3.20%	3.20%
Ready Capital Mortgage Financing 2018-FL2
Variable interest entities
Current Principal Balance	$ 80,042	$ 115,381
Carrying value	$ 79,202	$ 114,057
Weighted Average Rate	3.30%	3.80%
Ready Capital Mortgage Financing 2019-FL3
Variable interest entities
Current Principal Balance	$ 267,904	$ 267,904
Carrying value	$ 264,837	$ 264,249
Weighted Average Rate	3.00%	3.50%