Principles of Consolidation - Summary of Redwood's Interest in Third-Party Variable Interest Entity's (Details) - Real estate securities $ in Thousands	Dec. 31, 2017 USD ($)
Variable Interest Entity [Line Items]
Assets	$ 1,155,829
Senior IO Securities
Variable Interest Entity [Line Items]
Assets	177,191
Re-REMIC
Variable Interest Entity [Line Items]
Assets	38,875
Subordinate Securities
Variable Interest Entity [Line Items]
Assets	$ 939,763

Carrying amount of the assets in the reporting entity's statement of financial position that relate to the reporting entity's variable interest in the Variable Interest Entity (VIE), where the reporting entity is not the VIE's primary beneficiary.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph a
-URI http://asc.fasb.org/extlink&oid=64801991&loc=d3e5728-111685

Name:	us-gaap_VariableInterestEntityNonconsolidatedCarryingAmountAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant