INCOME TAXES - Income Tax Expense Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 31, 2019	Oct. 31, 2018	Oct. 31, 2019	Oct. 31, 2018
INCOME TAXES
Federal corporate income tax rate (as percent)			21.00%	21.00%
Computed expected income tax benefit (expense)			$ 8,070	$ (10,427)
Federal research and development tax credits				13,866
State income taxes, net of federal tax effect			185	676
Net operating loss deemed unrealizable			(6,280)	1,730
Bad debt loss			(5,026)
Foreign tax differential			(766)
Adjustments and other permanent differences			(1,299)	(1,336)
Income tax benefit	$ (1,996)	$ 12,560	4,936	$ 4,509
Deferred tax valuation allowance	$ 6,300		6,300
Total income tax benefit			$ 5,900