Principles of Consolidation - Securitization Activity Related to Unconsolidated Variable Interest Entity's Sponsored by Redwood (Details) - Variable Interest Entity, Not Primary Beneficiary - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Variable Interest Entity [Line Items]
Principal balance of loans transferred	$ 2,223,462	$ 1,872,910
Trading securities
Variable Interest Entity [Line Items]
Securities retained, at fair value	49,089	8,882
AFS Securities
Variable Interest Entity [Line Items]
Securities retained, at fair value	$ 4,187	$ 4,847