Principles of Consolidation - Key Assumptions and Sensitivity Analysis for Assets Retained from Unconsolidated Variable Interest Entity's Sponsored by Redwood (Detail) - Variable Interest Entity, Not Primary Beneficiary - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Mortgage servicing rights
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	$ 65,753	$ 56,801
Expected life (in years)	8 years	7 years
Prepayment speed assumption (annual CPR)	10.00%	14.00%
Decrease in fair value from:
10% adverse change	$ 2,780	$ 2,419
25% adverse change	$ 6,242	$ 5,639
Discount rate assumption	11.00%	11.00%
Decrease in fair value from:
100 basis point increase	$ 3,004	$ 2,104
200 basis point increase	5,514	4,102
Senior 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	$ 62,427	$ 93,802
Expected life (in years)	7 years	6 years
Prepayment speed assumption (annual CPR)	10.00%	9.00%
Decrease in fair value from:
10% adverse change	$ 1,920	$ 3,999
25% adverse change	$ 4,543	$ 9,475
Discount rate assumption	9.00%	8.00%
Decrease in fair value from:
100 basis point increase	$ 2,689	$ 4,214
200 basis point increase	$ 5,166	$ 8,091
Credit loss assumption	0.25%	0.25%
Decrease in fair value from:
10% higher losses	$ 241	$ 126
25% higher losses	316	299
Interest Only 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	40,000	88,000
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	$ 304,118	$ 460,990
Expected life (in years)	12 years	10 years
Prepayment speed assumption (annual CPR)	11.00%	10.00%
Decrease in fair value from:
10% adverse change	$ 825	$ 684
25% adverse change	$ 2,114	$ 2,355
Discount rate assumption	6.00%	5.00%
Decrease in fair value from:
100 basis point increase	$ 24,530	$ 34,149
200 basis point increase	$ 45,844	$ 64,474
Credit loss assumption	0.25%	0.25%
Decrease in fair value from:
10% higher losses	$ 19,746	$ 3,169
25% higher losses	$ 24,061	$ 7,841