Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Recurring Basis and Categorized using Fair Value Hierarchy (Detail) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Feb. 29, 2024	May 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available-for-sale debt securities	$ 27,371	$ 27,162
Total marketable equity securities	145,553	121,153
Assets (liabilities) at fair value	170,643	145,629
U.S. Treasury and other government
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available-for-sale debt securities	27,231	27,021
Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available-for-sale debt securities	140	141
Stocks | Foreign
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable equity securities	1,319	786
Stocks | Domestic
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable equity securities	10,794	5,009
Mutual funds | Foreign
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable equity securities	45,225	40,074
Mutual funds | Domestic
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable equity securities	88,215	75,284
Contingent consideration liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration	(2,281)	(2,686)
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable equity securities	12,113	5,795
Assets (liabilities) at fair value	12,113	5,795
Quoted Prices in Active Markets for Identical Assets (Level 1) | Stocks | Foreign
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable equity securities	1,319	786
Quoted Prices in Active Markets for Identical Assets (Level 1) | Stocks | Domestic
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable equity securities	10,794	5,009
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available-for-sale debt securities	27,371	27,162
Total marketable equity securities	133,440	115,358
Assets (liabilities) at fair value	160,811	142,520
Significant Other Observable Inputs (Level 2) | U.S. Treasury and other government
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available-for-sale debt securities	27,231	27,021
Significant Other Observable Inputs (Level 2) | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available-for-sale debt securities	140	141
Significant Other Observable Inputs (Level 2) | Mutual funds | Foreign
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable equity securities	45,225	40,074
Significant Other Observable Inputs (Level 2) | Mutual funds | Domestic
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable equity securities	88,215	75,284
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets (liabilities) at fair value	(2,281)	(2,686)
Significant Unobservable Inputs (Level 3) | Contingent consideration liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration	$ (2,281)	$ (2,686)