Mortgage Repurchase Facility - Additional information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2013	Jan. 31, 2013	Mar. 31, 2012
Lines Of Credit And Debt Obligations [Line Items]
Maximum aggregate commitment	$ 50,000,000	$ 80,000,000
Mortgage repurchase facility	$ 41,500,000		$ 76,300,000
Line of Credit facility, Interest Rate Description	Advances under the Mortgage Repurchase Facility carry a Pricing Rate equal to the greater of (i) the LIBOR Rate (as defined in the Mortgage Repurchase Facility) plus 2.5%, or (ii) 3.25%. The Mortgage Repurchase Facility contains various representations, warranties and affirmative and negative covenants customary for agreements of this type. The negative covenants include, among others, (i) an Adjusted Tangible Net Worth requirement, (ii) a minimum Adjusted Tangible Net Worth Ratio, (iii) an Adjusted Net Income requirement, and (iv) a minimum Liquidity requirement. The foregoing terms are defined in the Mortgage Repurchase Facility.
Minimum [Member]
Lines Of Credit And Debt Obligations [Line Items]
LIBOR basis spread	2.50%
Maximum [Member]
Lines Of Credit And Debt Obligations [Line Items]
LIBOR basis spread	3.25%