Principles of Consolidation - Summary of Redwood's Interest in Third-Party Variable Interest Entity's (Details) - REO - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Variable Interest Entity [Line Items]
Assets	$ 1,054,378	$ 1,176,161
Senior
Variable Interest Entity [Line Items]
Assets	141,264	185,107
Mezzanine
Variable Interest Entity [Line Items]
Assets	589,189	547,249
Subordinate
Variable Interest Entity [Line Items]
Assets	306,713	428,713
Total Mortgage-Backed Securities
Variable Interest Entity [Line Items]
Assets	1,037,166	1,161,069
Excess MSR
Variable Interest Entity [Line Items]
Assets	$ 17,212	$ 15,092