Loans at Fair Value and Notes and Certificates at Fair Value - Additional Information (Detail) (USD $)	9 Months Ended	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2013	Mar. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notes and certificates, payment frequency		Monthly
Notes and certificates, fixed interest rate minimum		5.42%
Notes and certificates, fixed interest rate maximum		26.06%
Notes and certificates, maturity date description		Various maturity dates through December 2018.
Net fair value adjustment gains/(losses)	$ (595,000)	$ (33,000)	$ (1,000)
Financing receivable recorded investment equal to greater than 90 days past due	6,400,000	15,600,000
Fair value of financing receivable held as assets 90 days or more past due	700,000	1,800,000
Notes And Certificates At Fair Value | Investment Income
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net fair value adjustment gains/(losses)	600,000	30,000	1,000
90 days
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of loans	576	1,464
Aggregate adverse fair value adjustments	$ 5,700,000	$ 13,800,000
Scenario 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notes and certificates term		P36M
Scenario 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notes and certificates term		P60M