CASH, CASH EQUIVALENTS AND INVESTMENTS - Available-for-Sale Securities (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Apr. 30, 2026	Apr. 30, 2025	Jan. 31, 2026
Cash and Cash Equivalents
Interest receivable	$ 2,900		$ 3,400
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	445,319		400,573
Gross Unrealized Gains	1,714		3,501
Gross Unrealized Losses	2,128		475
Estimated Fair Value	444,905		403,599
US Treasury notes
Available-for-sale securities
Amortized Cost, Due within one year	50,284		45,446
Amortized Cost, Due in one to three years	84,984		77,931
Amortized Cost, Due in three to five years	310,051		277,196
Gross Unrealized Gains, Due within one year	228		127
Gross Unrealized Gains, Due in one to three years	744		1,182
Gross Unrealized Gains, Due in three to five years	742		2,192
Gross Unrealized Losses, Due within one year			8
Gross Unrealized Losses, Due in one to three years	107		13
Gross Unrealized Losses, Due in three to five years	2,021		454
Estimated Fair Value, Due within one year	50,512		45,565
Estimated Fair Value, Due in one to three years	85,621		79,100
Estimated Fair Value, Due in three to five years	$ 308,772		$ 278,934