Fair Value - Summary of Assets and Liabilities in Each Level of Fair Value Hierarchy (Parenthetical) (Detail) (Reverse Loans Held For Sale [Member], USD $)	Jun. 30, 2013	Dec. 31, 2012
Reverse Loans Held For Sale [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Assets, Fair Value	$ 0	$ 28,500,000