Short-Term Borrowings - Commitments under Revolving Credit Agreements (Details) - Revolving credit agreements - USD ($) $ in Thousands		6 Months Ended	12 Months Ended
		Nov. 30, 2019	May 31, 2019
Revolving Credit Agreements
Maximum borrowing capacity		$ 2,725,000	$ 2,975,000
Letters of credit outstanding		3,000	3,000
Total available		2,722,000	2,972,000
Three Year Agreement
Revolving Credit Agreements
Maximum borrowing capacity		1,315,000	1,440,000
Total available		$ 1,315,000	$ 1,440,000
Debt Instrument, Maturity Date		Nov. 28, 2022	Nov. 28, 2021
Line of Credit Facility Commitment Fee Percentage (percent)	[1]	0.075%	0.075%
Five Year Agreement
Revolving Credit Agreements
Maximum borrowing capacity		$ 1,410,000	$ 1,535,000
Letters of credit outstanding		3,000	3,000
Total available		$ 1,407,000	$ 1,532,000
Debt Instrument, Maturity Date		Nov. 28, 2023	Nov. 28, 2023
Line of Credit Facility Commitment Fee Percentage (percent)	[1]	0.10%	0.10%

[1] Facility fee determined by CFC’s senior unsecured credit ratings based on the pricing schedules put in place at the inception of the related agreement.