Member Loans at Fair Value and Notes and Certificates at Fair Value - Additional Information (Detail) (USD $)	9 Months Ended				12 Months Ended	3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2013 Scenario 1	Sep. 30, 2013 Scenario 2	Sep. 30, 2013 90 days Loan	Dec. 31, 2012 90 days Loan	Sep. 30, 2013 Member Loans At Fair Value	Sep. 30, 2012 Member Loans At Fair Value	Sep. 30, 2013 Member Loans At Fair Value	Sep. 30, 2012 Member Loans At Fair Value	Sep. 30, 2013 Notes And Certificates At Fair Value Investment Income	Sep. 30, 2012 Notes And Certificates At Fair Value Investment Income	Sep. 30, 2013 Notes And Certificates At Fair Value Investment Income	Sep. 30, 2012 Notes And Certificates At Fair Value Investment Income
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notes and certificates term		P36M	P60M
Notes and certificates, payment frequency	Monthly
Notes and certificates, fixed interest rate minimum	6.03%
Notes and certificates, fixed interest rate maximum	26.06%
Notes and certificates, maturity date description	Various maturity dates through September 2018
Fair value assets measured on recurring basis gain and loss included in investment income						$ (15,600,000)	$ (7,200,000)	$ (37,900,000)	$ (15,600,000)
Net fair value adjustment gains/(losses)										(6,000)	(141,000)	(29,000)	(229,000)
Number of loans				1,097	576
Financing receivable recorded investment equal to greater than 90 days past due				12,300,000	6,400,000
Aggregate adverse fair value adjustments				10,900,000	5,700,000
Fair value of financing receivable held as assets 90 days or more past due				$ 1,400,000	$ 700,000