REVENUES FROM CONTRACTS WITH CUSTOMERS - Variable Consideration (Details) - USD ($) $ in Millions	3 Months Ended
Apr. 30, 2019	Jan. 31, 2019
REVENUES FROM CONTRACTS WITH CUSTOMERS
Amounts of unpriced change orders included in transaction prices	$ 21.7	$ 18.8
Increase in cost of project	27.6
Reversal of revenues previously recorded	$ 1.4

Amount of revenue recognized that was previously included in balance of obligation to transfer good or service to customer for which consideration from customer has been received or is due.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130549-203045

Name:	us-gaap_ContractWithCustomerLiabilityRevenueRecognized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration