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	Aug. 31, 2023	May 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available-for-sale debt securities	$ 26,120	$ 27,162
Total marketable equity securities	134,102	121,153
Assets (liabilities) at fair value	157,148	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	25,983	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	1,049	786
Stocks | Domestic
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable equity securities	9,742	5,009
Mutual funds | Foreign
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable equity securities	41,667	40,074
Mutual funds | Domestic
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable equity securities	81,644	75,284
Contingent consideration liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration	(3,074)	(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	10,791	5,795
Assets (liabilities) at fair value	10,791	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	1,049	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	9,742	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	26,120	27,162
Total marketable equity securities	123,311	115,358
Assets (liabilities) at fair value	149,431	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	25,983	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	41,667	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	81,644	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	(3,074)	(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	$ (3,074)	$ (2,686)