Fair Value of Financial Instruments - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands		Jun. 30, 2015	Dec. 31, 2014
Assets
Trading securities		$ 116,141	$ 111,606
Available-for-sale securities		1,041,458	1,267,624
Derivative assets	[1]	26,252	16,417
MSRs	[1]	168,462	139,293
Pledged collateral		10,194	9,927
Liabilities
Derivative liabilities	[1]	54,109	58,331
Commercial secured borrowings		65,232	$ 66,707
Fair Value, Measurements, Recurring
Assets
Trading securities		116,141
Available-for-sale securities		1,041,458
Derivative assets		26,252
MSRs		168,462
Pledged collateral		10,194
FHLBC stock		30,001
Guarantees asset		6,417
Liabilities
Derivative liabilities		54,109
Commercial secured borrowings		65,232
ABS issued		1,173,336
Fair Value, Measurements, Recurring | Residential Loans at Fair Value
Assets
Loans at fair value		3,285,022
Fair Value, Measurements, Recurring | Commercial Loans at Fair Value
Assets
Loans at fair value		235,616
Fair Value, Measurements, Recurring | Level 1
Assets
Derivative assets		7,625
Pledged collateral		10,194
FHLBC stock		30,001
Liabilities
Derivative liabilities		5,726
Fair Value, Measurements, Recurring | Level 2
Assets
Derivative assets		13,621
Liabilities
Derivative liabilities		43,983
Fair Value, Measurements, Recurring | Level 2 | Residential Loans at Fair Value
Assets
Loans at fair value		248,157
Fair Value, Measurements, Recurring | Level 3
Assets
Trading securities		116,141
Available-for-sale securities		1,041,458
Derivative assets		5,006
MSRs		168,462
Guarantees asset		6,417
Liabilities
Derivative liabilities		4,400
Commercial secured borrowings		65,232
ABS issued		1,173,336
Fair Value, Measurements, Recurring | Level 3 | Residential Loans at Fair Value
Assets
Loans at fair value		3,036,865
Fair Value, Measurements, Recurring | Level 3 | Commercial Loans at Fair Value
Assets
Loans at fair value		$ 235,616

[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 the primary beneficiary (Redwood Trust, Inc.). At June 30, 2015 and December 31, 2014, assets of consolidated VIEs totaled $1,622,636 and $1,900,208, respectively, and liabilities of consolidated VIEs totaled $1,263,249 and $1,546,490, respectively. See Note 4 for further discussion.