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, 2019	Dec. 31, 2018
Variable Interest Entity [Line Items]
Principal balance of loans transferred	$ 1,872,910	$ 3,188,358
Trading securities
Variable Interest Entity [Line Items]
Securities retained, at fair value	8,882	52,859
AFS Securities
Variable Interest Entity [Line Items]
Securities retained, at fair value	$ 4,847	$ 7,739