Principles of Consolidation - Assumptions Related to Assets Retained from Unconsolidated VIEs Sponsored by Redwood (Detail)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Mortgage Servicing Rights | Variable Interest Entity, Not Primary Beneficiary
Fair Value Assumption, Date of Securitization or Asset-backed Financing Arrangement, Transferor's Continuing Involvement, Servicing Assets or Liabilities [Line Items]
Discount rates	11.00%	11.00%
Mortgage Servicing Rights | Variable Interest Entity, Not Primary Beneficiary | Minimum
Fair Value Assumption, Date of Securitization or Asset-backed Financing Arrangement, Transferor's Continuing Involvement, Servicing Assets or Liabilities [Line Items]
Prepayment speeds	5.00%	5.00%
Mortgage Servicing Rights | Variable Interest Entity, Not Primary Beneficiary | Maximum
Fair Value Assumption, Date of Securitization or Asset-backed Financing Arrangement, Transferor's Continuing Involvement, Servicing Assets or Liabilities [Line Items]
Prepayment speeds	15.00%	16.00%
Senior Securities
Fair Value Assumption, Date of Securitization or Asset-backed Financing Arrangement, Transferor's Continuing Involvement, Servicing Assets or Liabilities [Line Items]
Fair Value Assumption, Date of Securitization or Asset-backed Financing Arrangement, Transferor's Continuing Involvement, Servicing Assets or Liabilities, Expected Credit Losses		0.25%
Senior Securities | Minimum
Fair Value Assumption, Date of Securitization or Asset-backed Financing Arrangement, Transferor's Continuing Involvement, Servicing Assets or Liabilities [Line Items]
Fair Value Assumption, Date of Securitization or Asset-backed Financing Arrangement, Transferor's Continuing Involvement, Servicing Assets or Liabilities, Expected Credit Losses	0.10%
Senior Securities | Maximum
Fair Value Assumption, Date of Securitization or Asset-backed Financing Arrangement, Transferor's Continuing Involvement, Servicing Assets or Liabilities [Line Items]
Fair Value Assumption, Date of Securitization or Asset-backed Financing Arrangement, Transferor's Continuing Involvement, Servicing Assets or Liabilities, Expected Credit Losses	0.25%
Senior Securities | Variable Interest Entity, Not Primary Beneficiary
Fair Value Assumption, Date of Securitization or Asset-backed Financing Arrangement, Transferor's Continuing Involvement, Servicing Assets or Liabilities [Line Items]
Discount rates	3.00%	3.00%
Senior Securities | Variable Interest Entity, Not Primary Beneficiary | Minimum
Fair Value Assumption, Date of Securitization or Asset-backed Financing Arrangement, Transferor's Continuing Involvement, Servicing Assets or Liabilities [Line Items]
Prepayment speeds	8.00%	8.00%
Senior Securities | Variable Interest Entity, Not Primary Beneficiary | Maximum
Fair Value Assumption, Date of Securitization or Asset-backed Financing Arrangement, Transferor's Continuing Involvement, Servicing Assets or Liabilities [Line Items]
Prepayment speeds	10.00%	10.00%
Subordinate Securities
Fair Value Assumption, Date of Securitization or Asset-backed Financing Arrangement, Transferor's Continuing Involvement, Servicing Assets or Liabilities [Line Items]
Fair Value Assumption, Date of Securitization or Asset-backed Financing Arrangement, Transferor's Continuing Involvement, Servicing Assets or Liabilities, Expected Credit Losses	0.25%	0.25%
Subordinate Securities | Minimum
Fair Value Assumption, Date of Securitization or Asset-backed Financing Arrangement, Transferor's Continuing Involvement, Servicing Assets or Liabilities [Line Items]
Fair Value Assumption, Date of Securitization or Asset-backed Financing Arrangement, Transferor's Continuing Involvement, Servicing Assets or Liabilities, Expected Credit Losses	0.10%
Subordinate Securities | Variable Interest Entity, Not Primary Beneficiary
Fair Value Assumption, Date of Securitization or Asset-backed Financing Arrangement, Transferor's Continuing Involvement, Servicing Assets or Liabilities [Line Items]
Discount rates	6.00%	5.00%
Subordinate Securities | Variable Interest Entity, Not Primary Beneficiary | Minimum
Fair Value Assumption, Date of Securitization or Asset-backed Financing Arrangement, Transferor's Continuing Involvement, Servicing Assets or Liabilities [Line Items]
Prepayment speeds	8.00%	8.00%
Subordinate Securities | Variable Interest Entity, Not Primary Beneficiary | Maximum
Fair Value Assumption, Date of Securitization or Asset-backed Financing Arrangement, Transferor's Continuing Involvement, Servicing Assets or Liabilities [Line Items]
Prepayment speeds	10.00%	10.00%