Loans - Payment Status of Loans Outstanding (Details) - USD ($) $ in Thousands		Nov. 30, 2019	May 31, 2019	Nov. 30, 2018
Payment Status of Loans
Past due		$ 0	$ 0
Total recorded investment in loans		26,426,879	25,905,664	$ 25,282,953
Non-accrual loans		$ 0	$ 0
As a % of total loans
Current (percent)		100.00%	100.00%
30-89 days past due (percent)		0.00%	0.00%
90 days or more past due (percent)	[1]	0.00%	0.00%
Total past due (percent)		0.00%	0.00%
Total financing receivables (percent)		100.00%	100.00%
Non-accrual loans (percent)		0.00%	0.00%
CFC
Payment Status of Loans
Past due		$ 0	$ 0
Total recorded investment in loans		25,368,276	24,817,676
Non-accrual loans		0	0
CFC | Distribution
Payment Status of Loans
Past due		0	0
Total recorded investment in loans		20,682,596	20,155,266
Non-accrual loans		0	0
CFC | Power supply
Payment Status of Loans
Past due		0	0
Total recorded investment in loans		4,601,783	4,578,841
Non-accrual loans		0	0
CFC | Statewide and associate
Payment Status of Loans
Total recorded investment in loans		83,897	83,569
NCSC
Payment Status of Loans
Past due		0	0
Total recorded investment in loans		702,279	742,888
Non-accrual loans		0	0
RTFC
Payment Status of Loans
Past due		0
Total recorded investment in loans		356,324	345,100
Non-accrual loans		0	0
Current
Payment Status of Loans
Current		26,426,879	25,905,664
Current | CFC
Payment Status of Loans
Current		25,368,276	24,817,676
Current | CFC | Distribution
Payment Status of Loans
Current		20,682,596	20,155,266
Current | CFC | Power supply
Payment Status of Loans
Current		4,601,783	4,578,841
Current | CFC | Statewide and associate
Payment Status of Loans
Current		83,897	83,569
Current | NCSC
Payment Status of Loans
Current		702,279	742,888
Current | RTFC
Payment Status of Loans
Current		356,324	345,100
30-89 Days Past Due
Payment Status of Loans
Past due		0	0
30-89 Days Past Due | CFC
Payment Status of Loans
Past due		0	0
30-89 Days Past Due | CFC | Distribution
Payment Status of Loans
Past due		0	0
30-89 Days Past Due | CFC | Power supply
Payment Status of Loans
Past due		0	0
30-89 Days Past Due | NCSC
Payment Status of Loans
Past due		0	0
30-89 Days Past Due | RTFC
Payment Status of Loans
Past due		0	0
90 Days or More Past Due
Payment Status of Loans
Past due	[1]	0	0
90 Days or More Past Due | CFC
Payment Status of Loans
Past due	[1]	0	0
90 Days or More Past Due | CFC | Distribution
Payment Status of Loans
Past due	[1]	0	0
90 Days or More Past Due | CFC | Power supply
Payment Status of Loans
Past due	[1]	0	0
90 Days or More Past Due | NCSC
Payment Status of Loans
Past due	[1]	$ 0	$ 0

[1] All loans 90 days or more past due are on nonaccrual status.