Derivative Instruments and Hedging Activities - Rating Triggers (Details) - USD ($) $ in Thousands	Feb. 28, 2023	May 31, 2022
Derivative [Line Items]
Notional Amount	$ 7,450,714	$ 8,061,631
Interest rate swaps
Derivative [Line Items]
Notional Amount	5,343,059
Payable Due from CFC	(2,291)
Receivable Due to CFC	295,367
Net Receivable (Payable)	293,076
Moody's, A3 Rating Standard Poor's A- Rating | Interest rate swaps
Derivative [Line Items]
Notional Amount	30,930
Payable Due from CFC	(1,292)
Receivable Due to CFC	0
Net Receivable (Payable)	(1,292)
Moodys Baa 1 Rating Standard Poor's BBB Plus Rating | Interest rate swaps
Derivative [Line Items]
Notional Amount	4,992,690
Payable Due from CFC	(999)
Receivable Due to CFC	273,349
Net Receivable (Payable)	272,350
Moody's Baa 2 Rating Standard Poor's BBB Rating | Interest rate swaps
Derivative [Line Items]
Notional Amount	319,439
Payable Due from CFC	0
Receivable Due to CFC	22,018
Net Receivable (Payable)	$ 22,018