Recorded Investment in Residential Loans Held-For-Investment Organized by Year of Origination (Detail) (Residential Loans Held for Investment, USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Financing Receivable, Recorded Investment [Line Items]
Residential loans	$ 2,021,328	$ 2,301,316
2003 & Earlier
Financing Receivable, Recorded Investment [Line Items]
Residential loans	1,017,135	1,131,200
2004
Financing Receivable, Recorded Investment [Line Items]
Residential loans	545,935	569,379
2005
Financing Receivable, Recorded Investment [Line Items]
Residential loans	67,266	71,792
2006
Financing Receivable, Recorded Investment [Line Items]
Residential loans	157,349	164,333
2009
Financing Receivable, Recorded Investment [Line Items]
Residential loans	37,823	58,628
2010
Financing Receivable, Recorded Investment [Line Items]
Residential loans	121,581	197,964
2011
Financing Receivable, Recorded Investment [Line Items]
Residential loans	$ 74,239	$ 108,020