INCOME TAXES - Research and Development Tax Credits (Details) - USD ($) $ in Millions	3 Months Ended
Apr. 30, 2019	Jan. 31, 2019	Oct. 31, 2017
INCOME TAXES
Period for identify and quantify the amounts of research and development credits	3 years
Research and development tax credit benefit			$ 16.6
Unrecognized income tax benefits related to research and development credits	$ 5.2
Amount of liability		$ 5.1

Amount before allocation of valuation allowances of deferred tax asset attributable to deductible research tax credit carryforwards.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32632-109319

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32559-109319

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32621-109319

Name:	us-gaap_DeferredTaxAssetsTaxCreditCarryforwardsResearch
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant