Receivables - Loans Receivable by Internal Credit Rating (Detail) (USD $)	9 Months Ended	12 Months Ended
	Sep. 30, 2013 Number	Dec. 31, 2012 Number
Financing Receivable, Recorded Investment [Line Items]
Number of Loans	14	18
Carrying Value of Loans Receivable	$ 108,163,000	$ 211,250,000
Greater than Zero [Member]
Financing Receivable, Recorded Investment [Line Items]
Number of Loans	13	18
Carrying Value of Loans Receivable	97,840,000	211,250,000
Equal to Zero [Member]
Financing Receivable, Recorded Investment [Line Items]
Number of Loans	1
Carrying Value of Loans Receivable	10,323,000
Less than Zero [Member]
Financing Receivable, Recorded Investment [Line Items]
Number of Loans
Carrying Value of Loans Receivable