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	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Variable Interest Entity [Line Items]
Principal balance of loans transferred	$ 366,999	$ 327,511	$ 1,116,092	$ 2,735,644
Trading securities retained, at fair value
Variable Interest Entity [Line Items]
Securities retained, at fair value	1,228	2,583	4,736	48,831
AFS securities retained, at fair value
Variable Interest Entity [Line Items]
Securities retained, at fair value	$ 1,069	$ 776	$ 3,023	$ 6,728