Loans and Commitments Loans - Internal Risk Rating (Details) - USD ($) $ in Thousands	May 31, 2016		May 31, 2015
Credit Quality
Loans and Leases Receivable, Net of Deferred Income	$ 23,152,517	[1],[2]	$ 21,459,220
CFC
Credit Quality
Loans and Leases Receivable, Net of Deferred Income	22,129,873	[1]	20,341,990
CFC | Distribution
Credit Quality
Loans and Leases Receivable, Net of Deferred Income	17,674,335		16,095,043
CFC | Power supply
Credit Quality
Loans and Leases Receivable, Net of Deferred Income	4,401,185		4,181,481
CFC | Statewide and associate
Credit Quality
Loans and Leases Receivable, Net of Deferred Income	54,353		65,466
RTFC
Credit Quality
Loans and Leases Receivable, Net of Deferred Income	341,842		385,709
NCSC
Credit Quality
Loans and Leases Receivable, Net of Deferred Income	680,802		731,521
Pass
Credit Quality
Loans and Leases Receivable, Net of Deferred Income	23,104,932		21,409,443
Pass | CFC
Credit Quality
Loans and Leases Receivable, Net of Deferred Income	22,096,213		20,309,197
Pass | CFC | Distribution
Credit Quality
Loans and Leases Receivable, Net of Deferred Income	17,640,928		16,062,516
Pass | CFC | Power supply
Credit Quality
Loans and Leases Receivable, Net of Deferred Income	4,401,185		4,181,481
Pass | CFC | Statewide and associate
Credit Quality
Loans and Leases Receivable, Net of Deferred Income	54,100		65,200
Pass | RTFC
Credit Quality
Loans and Leases Receivable, Net of Deferred Income	330,167		373,087
Pass | NCSC
Credit Quality
Loans and Leases Receivable, Net of Deferred Income	678,552		727,159
Criticized
Credit Quality
Loans and Leases Receivable, Net of Deferred Income	47,585		49,777
Criticized | CFC
Credit Quality
Loans and Leases Receivable, Net of Deferred Income	33,660		32,793
Criticized | CFC | Distribution
Credit Quality
Loans and Leases Receivable, Net of Deferred Income	33,407		32,527
Criticized | CFC | Power supply
Credit Quality
Loans and Leases Receivable, Net of Deferred Income	0		0
Criticized | CFC | Statewide and associate
Credit Quality
Loans and Leases Receivable, Net of Deferred Income	253		266
Criticized | RTFC
Credit Quality
Loans and Leases Receivable, Net of Deferred Income	11,675		12,622
Criticized | NCSC
Credit Quality
Loans and Leases Receivable, Net of Deferred Income	$ 2,250		$ 4,362

[1] Includes nonperforming and restructured loans.

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