Short-Term Debt - Outstanding Balances of Short-Term Debt by Type of Collateral Securing Debt (Details)		12 Months Ended
		Dec. 31, 2017 USD ($) Facility	Dec. 31, 2016 USD ($) Facility
Short-term Debt [Line Items]
Number of Facilities | Facility			11
Outstanding Balance	[1],[2]	$ 1,938,682,000	$ 791,539,000
Line of Credit
Short-term Debt [Line Items]
Number of Facilities | Facility		13
Outstanding Balance		$ 1,688,412,000
Convertible notes, net
Short-term Debt [Line Items]
Outstanding Balance		$ 250,270,000
Weighted Average Interest Rate		4.63%
Weighted Average Days Until Maturity		105 days
Residential loan warehouse | Line of Credit
Short-term Debt [Line Items]
Number of Facilities | Facility		4	4
Outstanding Balance		$ 1,039,666,000	$ 485,544,000
Limit		$ 1,575,000,000	$ 1,325,000,000
Weighted Average Interest Rate		3.17%	2.40%
Weighted Average Days Until Maturity		197 days	206 days
Real estate securities repo | Line of Credit
Short-term Debt [Line Items]
Number of Facilities | Facility		9	7
Outstanding Balance		$ 648,746,000	$ 305,995,000
Limit		$ 0	$ 0
Weighted Average Interest Rate		2.69%	1.91%
Weighted Average Days Until Maturity		28 days	24 days

[1] Includes $250 million of convertible notes, which were reclassified from Long-term debt, net to Short-term debt as the maturity of the notes was less than one year as of December 31, 2017. See Note 11 for further discussion.

[2] Our consolidated balance sheets include assets of consolidated variable interest entities (“VIEs”) that can only be used to settle obligations of these VIEs and liabilities of consolidated VIEs for which creditors do not have recourse to Redwood Trust, Inc. or its affiliates. At December 31, 2017 and December 31, 2016, assets of consolidated VIEs totaled $1,259,774 and $798,317, respectively. At December 31, 2017 and December 31, 2016, liabilities of consolidated VIEs totaled $1,167,157 and $773,980, respectively. See Note 4 for further discussion.