Loans and Commitments (Details 8) - USD ($) $ in Thousands		Feb. 29, 2016		May. 31, 2015		Feb. 28, 2015
Loan Security
Total loans outstanding		$ 23,134,215	[1],[2]	$ 21,459,220	[1],[2]	$ 21,202,399
Loans receivable as a percentage of total loan (percent)		100.00%		100.00%
CFC
Loan Security
Total loans outstanding	[1]	$ 22,079,012		$ 20,341,990
RTFC
Loan Security
Total loans outstanding	[1]	357,967		385,709
NCSC
Loan Security
Total loans outstanding	[1]	697,236		731,521
Long-term fixed-rate loans
Loan Security
Total loans outstanding	[1]	21,127,042		19,543,274
Long-term variable-rate loans
Loan Security
Total loans outstanding	[1]	718,193		698,495
Loans guaranteed by RUS
Loan Security
Total loans outstanding	[1]	174,990		179,241
Line of credit loans
Loan Security
Total loans outstanding	[1]	$ 1,113,990		$ 1,038,210

[1] Includes nonperforming and restructured loans.

[2] Represents the unpaid principal balance excluding deferred loan origination costs.