Fair Value Measurement (Details 1) (Level 3, USD $) In Thousands, unless otherwise specified	Feb. 28, 2014	May 31, 2013
Level 3
Nonperforming loans, net of specific reserves	$ 10,331	$ 12,070

This element represents the portion of the recorded investment in financing receivables that are on nonaccrual status valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure.

No definition available.

Name:	nru_FinancingReceivableRecordedInvestmentNonperformingStatusNetOfReserveFairValueDisclosure
Namespace Prefix:	nru_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant