Loans Receivable, At Fair Value - Overall Statistics for Loans Receivable Portfolio Held at Fair Value (Parenthetical) (Detail) (LIBOR [Member])	Sep. 30, 2013	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
LIBOR Loans rate	0.18%	0.21%
Floating Rate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
LIBOR Loans rate	0.18%
Minimum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
LIBOR floor rate	0.20%
Minimum [Member] | Floating Rate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
LIBOR floor rate	2.00%