Residential Loans - Summary of Classifications and Carrying Value of Residential Loans (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Mortgage Loans on Real Estate [Line Items]
Residential loans	$ 3,286,480	$ 3,398,573
Residential Loans at Fair Value | Conforming Loan
Mortgage Loans on Real Estate [Line Items]
Residential loans	248,157	244,714
Residential Loans at Fair Value | Jumbo Loan
Mortgage Loans on Real Estate [Line Items]
Residential loans	642,466	1,096,317
Residential Loans at Lower of Cost or Fair Value
Mortgage Loans on Real Estate [Line Items]
Residential loans	1,458	1,488
Residential Loans Held For Investment at Fair Value
Mortgage Loans on Real Estate [Line Items]
Residential loans	1,160,000
Residential Loans Held For Investment at Fair Value | Jumbo Loan
Mortgage Loans on Real Estate [Line Items]
Residential loans	2,394,399	581,668
Residential Loans Held For Investment At Amortized Cost
Mortgage Loans on Real Estate [Line Items]
Residential loans		1,474,386
Redwood
Mortgage Loans on Real Estate [Line Items]
Residential loans	2,049,366	1,924,187
Redwood | Residential Loans at Fair Value | Conforming Loan
Mortgage Loans on Real Estate [Line Items]
Residential loans	248,157	244,714
Redwood | Residential Loans at Fair Value | Jumbo Loan
Mortgage Loans on Real Estate [Line Items]
Residential loans	642,466	1,096,317
Redwood | Residential Loans at Lower of Cost or Fair Value
Mortgage Loans on Real Estate [Line Items]
Residential loans	1,458	1,488
Redwood | Residential Loans Held For Investment at Fair Value | Jumbo Loan
Mortgage Loans on Real Estate [Line Items]
Residential loans	1,157,285	581,668
Redwood | Residential Loans Held For Investment At Amortized Cost
Mortgage Loans on Real Estate [Line Items]
Residential loans		0
Sequoia
Mortgage Loans on Real Estate [Line Items]
Residential loans	1,237,114	1,474,386
Sequoia | Residential Loans at Fair Value | Conforming Loan
Mortgage Loans on Real Estate [Line Items]
Residential loans	0	0
Sequoia | Residential Loans at Fair Value | Jumbo Loan
Mortgage Loans on Real Estate [Line Items]
Residential loans	0	0
Sequoia | Residential Loans at Lower of Cost or Fair Value
Mortgage Loans on Real Estate [Line Items]
Residential loans	0	0
Sequoia | Residential Loans Held For Investment at Fair Value | Jumbo Loan
Mortgage Loans on Real Estate [Line Items]
Residential loans	$ 1,237,114	0
Sequoia | Residential Loans Held For Investment At Amortized Cost
Mortgage Loans on Real Estate [Line Items]
Residential loans		$ 1,474,386