Derivative Financial Instruments - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended				3 Months Ended		6 Months Ended				3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012	Jun. 30, 2013 Interest Rate Swaps Maximum	Jun. 30, 2013 Cash Flow Hedging Interest Rate Swaps	Jun. 30, 2012 Cash Flow Hedging Interest Rate Swaps	Jun. 30, 2013 Cash Flow Hedging Interest Rate Swaps	Jun. 30, 2012 Cash Flow Hedging Interest Rate Swaps	Dec. 31, 2011 Cash Flow Hedging Interest Rate Swaps	Dec. 31, 2010 Cash Flow Hedging Interest Rate Swaps	Jun. 30, 2013 Unsecuritized Residential and Commercial Loans	Jun. 30, 2012 Unsecuritized Residential and Commercial Loans	Jun. 30, 2013 Unsecuritized Residential and Commercial Loans	Jun. 30, 2012 Unsecuritized Residential and Commercial Loans	Jun. 30, 2013 Unsecuritized Residential and Commercial Loans Interest Rate Contract	Jun. 30, 2013 Unsecuritized Residential and Commercial Loans Futures	Jun. 30, 2013 Unsecuritized Residential and Commercial Loans TBAs	Jun. 30, 2012 Not Designated as Hedging Instrument Interest Rate Swaps	Jun. 30, 2013 Redwood Contract
Derivative [Line Items]
Notional Amount	$ 2,537,000,000		$ 2,537,000,000		$ 1,453,000,000						$ 165,000,000	$ 165,000,000					$ 1,700,000,000	$ 268,000,000	$ 450,000,000	$ 26,000,000
Valuation adjustments on derivatives							14,000,000	(16,000,000)	21,000,000	(3,000,000)			50,000,000	(3,000,000)	51,000,000	(7,000,000)
Net unrealized losses on interest rate agreements accounted for as cash flow hedges	27,000,000		27,000,000		48,000,000
Hedges decreased in value recorded as a component of interest expense	69,000	1,000,000	157,000	2,000,000
Accumulated other comprehensive loss that will be amortized into interest expense						$ (1,000,000)
Number of outstanding derivative agreements with counterparties																					6