Subsequent Events - Additional Information (Detail) (Subsequent Event, USD $) In Thousands, unless otherwise specified	Jul. 31, 2013
Subsequent Event [Line Items]
Real estate investment reserved	$ 64,238
Commercial Mortgage Backed Securities
Subsequent Event [Line Items]
Real estate investment	135,000
Investment Grade Senior Notes
Subsequent Event [Line Items]
Real estate investment	101,250
Real estate investment advance rate	75.00%
Maturity date of investment	2029-01
Investment Grade Senior Notes | Upon Occurrence Of Certain Events
Subsequent Event [Line Items]
Maturity date of investment	2015-08
London Interest Bank Offer Rate
Subsequent Event [Line Items]
Weighted average rate above LIBOR rate	1.85%
Equity interest
Subsequent Event [Line Items]
Real estate investment	33,750
Collateralized Securities
Subsequent Event [Line Items]
Real estate investment	$ 70,762