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	Nov. 30, 2023	May 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available-for-sale debt securities	$ 27,018	$ 27,162
Total marketable equity securities	135,065	121,153
Assets (liabilities) at fair value	159,785	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	26,881	27,021
Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available-for-sale debt securities	137	141
Stocks | Foreign
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable equity securities	1,146	786
Stocks | Domestic
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable equity securities	9,791	5,009
Mutual funds | Foreign
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable equity securities	42,103	40,074
Mutual funds | Domestic
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable equity securities	82,025	75,284
Contingent consideration liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration	(2,298)	(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	10,937	5,795
Assets (liabilities) at fair value	10,937	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	1,146	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	9,791	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	27,018	27,162
Total marketable equity securities	124,128	115,358
Assets (liabilities) at fair value	151,146	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	26,881	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	137	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	42,103	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	82,025	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	(2,298)	(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	$ (2,298)	$ (2,686)