CASH, CASH EQUIVALENTS AND INVESTMENTS - Available-for-Sale Securities (Details) - USD ($) $ in Thousands	3 Months Ended
	Apr. 30, 2025	Apr. 30, 2024	Jan. 31, 2025
Cash and Cash Equivalents
Interest receivable	$ 1,700		$ 2,100
Debt Securities, Available-for-Sale, Accrued Interest, after Allowance for Credit Loss, Current, Statement of Financial Position [Extensible Enumeration]	Investments		Investments
Proceeds from sale of debt securities, available-for-sale	$ 0	$ 0
Amounts of gains or losses reclassified out of other comprehensive income	0	$ 0
Available-for-sale securities
Amortized Cost	239,014		$ 227,156
Gross Unrealized Gains	3,442		631
Gross Unrealized Losses	298		1,042
Estimated Fair Value	242,158		226,745
US Treasury notes
Available-for-sale securities
Amortized Cost, Due within one year	50,463		50,676
Amortized Cost, Due in one to three years	76,240		84,881
Amortized Cost, Due in three to five years	112,311		91,599
Gross Unrealized Gains, Due within one year	76		126
Gross Unrealized Gains, Due in one to three years	1,141		381
Gross Unrealized Gains, Due in three to five years	2,225		124
Gross Unrealized Losses, Due within one year	27		7
Gross Unrealized Losses, Due in one to three years			105
Gross Unrealized Losses, Due in three to five years	271		930
Estimated Fair Value, Due within one year	50,512		50,795
Estimated Fair Value, Due in one to three years	77,381		85,157
Estimated Fair Value, Due in three to five years	$ 114,265		$ 90,793