Postretirement Benefits - Additional Information (Detail) $ in Millions	May 31, 2023 USD ($)
Schedule of Pension and Other Postretirement Benefits Expected Benefit Payments [Line Items]
Estimated benefits payable in the first year	$ 64.2
Estimated benefits payable in the second year	69.5
Estimated benefits payable in the third year	74.6
Estimated benefits payable in the fourth year	76.7
Estimated benefits payable in the fifth year	81.8
Estimated benefits payable in the years thereafter	416.7
Postretirement Benefits
Schedule of Pension and Other Postretirement Benefits Expected Benefit Payments [Line Items]
Estimated benefits payable in the years thereafter	9.4
Minimum | Postretirement Benefits
Schedule of Pension and Other Postretirement Benefits Expected Benefit Payments [Line Items]
Estimated benefits payable in the first year	1.2
Estimated benefits payable in the second year	1.2
Estimated benefits payable in the third year	1.2
Estimated benefits payable in the fourth year	1.2
Estimated benefits payable in the fifth year	1.2
Maximum | Postretirement Benefits
Schedule of Pension and Other Postretirement Benefits Expected Benefit Payments [Line Items]
Estimated benefits payable in the first year	1.6
Estimated benefits payable in the second year	1.6
Estimated benefits payable in the third year	1.6
Estimated benefits payable in the fourth year	1.6
Estimated benefits payable in the fifth year	$ 1.6