Derivative Instruments and Hedging Activities - Rating Triggers (Details) - USD ($) $ in Thousands	Aug. 31, 2022	May 31, 2022
Derivative [Line Items]
Notional Amount	$ 7,979,761	$ 8,061,631
Interest rate swaps
Derivative [Line Items]
Notional Amount	5,813,296
Payable Due from CFC	(12,301)
Receivable Due to CFC	142,964
Net Receivable (Payable)	130,663
Moody's, A3 Rating Standard Poor's A- Rating | Interest rate swaps
Derivative [Line Items]
Notional Amount	36,110
Payable Due from CFC	(2,944)
Receivable Due to CFC	0
Net Receivable (Payable)	(2,944)
Moodys Baa 1 Rating Standard Poor's BBB Plus Rating | Interest rate swaps
Derivative [Line Items]
Notional Amount	5,454,822
Payable Due from CFC	(9,357)
Receivable Due to CFC	131,658
Net Receivable (Payable)	122,301
Moody's Baa 2 Rating Standard Poor's BBB Rating | Interest rate swaps
Derivative [Line Items]
Notional Amount	322,364
Payable Due from CFC	0
Receivable Due to CFC	11,306
Net Receivable (Payable)	$ 11,306