Principles of Consolidation - Cash Flows 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, 2018	Dec. 31, 2017
Variable Interest Entity [Line Items]
Proceeds from new transfers	$ 3,175,900	$ 2,563,499
MSR fees received	13,417	14,302
Funding of compensating interest, net	(122)	(151)
Cash flows received on retained securities	$ 28,614	$ 27,156