Derivative Instruments and Hedging Activities - Derivatives Offsetting (Details) - USD ($) $ in Thousands	Feb. 28, 2022	May 31, 2021
Derivative [Line Items]
Derivative asset, fair value, amount not offset against collateral	$ 50,901	$ 121,259
Derivative liability, fair value, amount not offset against collateral	391,988	584,989
Interest rate swaps
Derivative [Line Items]
Derivative asset, fair value, gross asset	50,901	121,259
Derivative asset, fair value, gross liability	0	0
Derivative asset, fair value, amount not offset against collateral	50,901	121,259
Derivative, collateral, obligation to return securities	50,901	121,259
Derivative, collateral, obligation to return cash	0	0
Derivative asset, fair value, amount offset against collateral	0	0
Derivative liability, fair value, gross liability	391,988	584,989
Derivative liability, fair value, gross asset	0	0
Derivative liability, fair value, amount not offset against collateral	391,988	584,989
Derivative, collateral, right to reclaim securities	50,901	121,259
Derivative, collateral, right to reclaim cash	0	0
Derivative liability, fair value, amount offset against collateral	$ 341,087	$ 463,730