Fair Values of Member Loans and Notes (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Member Loans at fair value	$ 1,516,676	$ 781,215
Notes and Certificates at fair value	1,522,975	785,316
Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Member Loans at fair value	1,516,676	781,215
Notes and Certificates at fair value	$ 1,522,975	$ 785,316