Mortgage Servicing Rights - Activity for Residential First-Lien Mortgage Servicing Rights (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Servicing Asset at Fair Value, Amount [Roll Forward]
Balance at beginning of period	[1]	$ 118,526
Additions		7,387	$ 10,060	$ 64,725
Balance at End of Period	[1]	63,598	118,526
MSRs
Servicing Asset at Fair Value, Amount [Roll Forward]
Balance at beginning of period		118,526	191,976	139,293
Additions		8,026	25,362	95,281
Sales		(52,788)	(62,440)	(18,206)
Changes in fair value due to: Changes in assumptions		(1,088)	(14,512)	(5,453)
Changes in fair value due to: Other changes		(9,078)	(21,860)	(18,939)
Balance at End of Period		$ 63,598	$ 118,526	$ 191,976

[1] 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.