v3.26.3
Fair Value - Assets Measured at Fair Value on Non-Recurring Basis (Detail) - Fair Value, Nonrecurring - USD ($)
Aug. 31, 2026
May 31, 2026
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Assets, Fair Value Disclosure $ 0 $ 77,300,000
Long-Lived Assets, Intangible Assets, and Other Assets - Electrical Steel    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Assets, Fair Value Disclosure [1]   76,800,000
Long-Lived Assets Held and Used - Taylor    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Assets, Fair Value Disclosure [2]   500,000
Fair Value, Inputs, Level 1    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Assets, Fair Value Disclosure   0
Fair Value, Inputs, Level 1 | Long-Lived Assets, Intangible Assets, and Other Assets - Electrical Steel    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Assets, Fair Value Disclosure [1]   0
Fair Value, Inputs, Level 1 | Long-Lived Assets Held and Used - Taylor    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Assets, Fair Value Disclosure [2]   0
Fair Value, Inputs, Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Assets, Fair Value Disclosure   0
Fair Value, Inputs, Level 2 | Long-Lived Assets, Intangible Assets, and Other Assets - Electrical Steel    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Assets, Fair Value Disclosure [1]   0
Fair Value, Inputs, Level 2 | Long-Lived Assets Held and Used - Taylor    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Assets, Fair Value Disclosure [2]   0
Fair Value, Inputs, Level 3    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Assets, Fair Value Disclosure   77,300,000
Fair Value, Inputs, Level 3 | Long-Lived Assets, Intangible Assets, and Other Assets - Electrical Steel    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Assets, Fair Value Disclosure [1]   76,800,000
Fair Value, Inputs, Level 3 | Long-Lived Assets Held and Used - Taylor    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Assets, Fair Value Disclosure [2]   $ 500,000
[1] During fiscal 2026, the Company measured the fair values of certain long-lived asset groups and the Electrical Steel reporting unit in connection with the impairment analyses performed. These fair value measurements were classified within Level 3 of the fair value hierarchy because they included significant unobservable inputs. The fair values of the affected long-lived asset groups were determined using a discounted cash flow method, market approach, cost approach, or combination thereof, which included significant unobservable inputs.
[2] During fiscal 2026, the net book value of certain machinery at the manufacturing facility in Taylor, Michigan was lowered to $0.5 million based on prices for similar assets.