Loans Receivable - Allocation of Loans Receivable by Both Loan Type and Internal Risk Ratings (Parenthetical) (Detail) (Senior Mortgages Loans [Member], USD $) In Millions, unless otherwise specified	Jun. 30, 2013
Senior Mortgages Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Mortgages with aggregate principal balance and net book value	$ 91.1