RECENTLY ISSUED ACCOUNTING PRONOUNCEMENTS (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 31, 2016	Oct. 31, 2015	Oct. 31, 2016	Oct. 31, 2015	Jan. 31, 2016
Recently issued accounting pronouncements
Income tax expense	$ 8,194	$ 7,045	$ 27,122	$ 19,845
Deferred income tax liabilities, noncurrent					$ 224
Accounting Standards Update ('ASU') 2016-09 - Reduction in income tax expense: Improvements to Employee Share-Based Payment Accounting | Adjustment
Recently issued accounting pronouncements
Income tax expense	(2,000)		(3,000)
Accounting Standards Update ("ASU") 2015-17 - Income Taxes: Balance Sheet Classification of Deferred Taxes | Retrospective early adoption
Recently issued accounting pronouncements
Deferred income tax liabilities, noncurrent					(1,100)
Deferred tax assets, Current					$ (1,100)
Costs of revenues
Recently issued accounting pronouncements
Rent expense	$ 3,300	$ 3,100	$ 9,100	$ 11,500