Principles of Consolidation - Key Assumptions and Sensitivity Analysis for Assets Retained from 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	Dec. 31, 2020	Dec. 31, 2019
MSRs
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Fair value	$ 8,413	$ 40,254	$ 8,413	$ 40,254
Expected life (in years)	2 years	6 years
Prepayment speed assumption (annual CPR)	37.00%	11.00%
Decrease in fair value from:
10% adverse change	$ 906	$ 1,643	906	1,643
25% adverse change	$ 2,058	$ 3,913	2,058	3,913
Discount rate assumption	12.00%	11.00%
Decrease in fair value from:
100 basis point increase	$ 196	$ 1,447	196	1,447
200 basis point increase	380	2,795	$ 380	$ 2,795
MSRs | Minimum
Decrease in fair value from:
Impact of adverse change in prepayment speed			10.00%	10.00%
Decrease in fair value from:
Impact of increase in discount rate assumption			1.00%	1.00%
Decrease in fair value from:
Impact of adverse change in expected credit losses			10.00%	10.00%
MSRs | Maximum
Decrease in fair value from:
Impact of adverse change in prepayment speed			25.00%	25.00%
Decrease in fair value from:
Impact of increase in discount rate assumption			2.00%	2.00%
Decrease in fair value from:
Impact of adverse change in expected credit losses			25.00%	25.00%
Senior IO Securities
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Fair value	$ 17,333	$ 48,765	$ 17,333	$ 48,765
Expected life (in years)	3 years	6 years
Prepayment speed assumption (annual CPR)	31.00%	14.00%
Decrease in fair value from:
10% adverse change	$ 1,557	$ 1,908	1,557	1,908
25% adverse change	$ 3,754	$ 5,086	3,754	5,086
Discount rate assumption	21.00%	12.00%
Decrease in fair value from:
100 basis point increase	$ 337	$ 1,079	337	1,079
200 basis point increase	$ 659	$ 2,482	659	2,482
Credit loss assumption	0.41%	0.21%
Decrease in fair value from:
10% higher losses	$ 0	$ 0	0	0
25% higher losses	0	0	$ 0	$ 0
Senior IO Securities | Minimum
Decrease in fair value from:
Impact of adverse change in prepayment speed			10.00%	10.00%
Decrease in fair value from:
Impact of increase in discount rate assumption			1.00%	1.00%
Decrease in fair value from:
Impact of adverse change in expected credit losses			10.00%	10.00%
Senior IO Securities | Maximum
Decrease in fair value from:
Impact of adverse change in prepayment speed			25.00%	25.00%
Decrease in fair value from:
Impact of increase in discount rate assumption			2.00%	2.00%
Decrease in fair value from:
Impact of adverse change in expected credit losses			25.00%	25.00%
Subordinate Securities
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Fair value	$ 140,124	$ 180,309	$ 140,124	$ 180,309
Expected life (in years)	8 years	14 years
Prepayment speed assumption (annual CPR)	33.00%	16.00%
Decrease in fair value from:
10% adverse change	$ 452	$ 205	452	205
25% adverse change	$ 2,298	$ 1,434	2,298	1,434
Discount rate assumption	5.00%	5.00%
Decrease in fair value from:
100 basis point increase	$ 9,769	$ 18,127	9,769	18,127
200 basis point increase	$ 18,650	$ 33,630	18,650	33,630
Credit loss assumption	0.41%	0.21%
Decrease in fair value from:
10% higher losses	$ 2,409	$ 1,804	2,409	1,804
25% higher losses	$ 5,915	$ 4,520	$ 5,915	$ 4,520
Subordinate Securities | Minimum
Decrease in fair value from:
Impact of adverse change in prepayment speed			10.00%	10.00%
Decrease in fair value from:
Impact of increase in discount rate assumption			1.00%	1.00%
Decrease in fair value from:
Impact of adverse change in expected credit losses			10.00%	10.00%
Subordinate Securities | Maximum
Decrease in fair value from:
Impact of adverse change in prepayment speed			25.00%	25.00%
Decrease in fair value from:
Impact of increase in discount rate assumption			2.00%	2.00%
Decrease in fair value from:
Impact of adverse change in expected credit losses			25.00%	25.00%