Summary of Classifications and Carrying Value of Residential Loans (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Mortgage Loans on Real Estate [Line Items]
Residential loans	$ 2,592,532	$ 2,835,470
Residential Loans at Fair Value
Mortgage Loans on Real Estate [Line Items]
Residential loans	726,161	553,576
Residential Loans at Lower of Cost or Fair Value
Mortgage Loans on Real Estate [Line Items]
Residential loans	1,718	9,082
Residential Loans Held for Investment
Mortgage Loans on Real Estate [Line Items]
Residential loans	1,864,653	2,272,812
Redwood
Mortgage Loans on Real Estate [Line Items]
Residential loans	727,879	562,658
Redwood | Residential Loans at Fair Value
Mortgage Loans on Real Estate [Line Items]
Residential loans	726,161	553,576
Redwood | Residential Loans at Lower of Cost or Fair Value
Mortgage Loans on Real Estate [Line Items]
Residential loans	1,718	9,082
Sequoia
Mortgage Loans on Real Estate [Line Items]
Residential loans	1,864,653	2,272,812
Sequoia | Residential Loans Held for Investment
Mortgage Loans on Real Estate [Line Items]
Residential loans	$ 1,864,653	$ 2,272,812