Investments in Securities and Security-Related Receivables (Parenthetical) (Detail) (CMBS receivables, Security-related receivables, USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Standard & Poor's AAA and A- Rating
Investment Securities [Line Items]
Securities, fair value	$ 8,228	$ 8,398
Standard & Poor's BBB+ and B- Rating
Investment Securities [Line Items]
Securities, fair value	26,594	26,013
Standard & Poor's, CCC Rating
Investment Securities [Line Items]
Securities, fair value	8,164	8,782
Standard & Poor's, D Rating
Investment Securities [Line Items]
Securities, fair value	$ 1,132	$ 617