REVENUE RECOGNITION REVENUE RECOGNITION - IMPACT OF ADOPTION - ADDITIONAL INFORMATION (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
	Feb. 01, 2018	Jan. 31, 2019	Oct. 31, 2018	Jul. 31, 2018	Apr. 30, 2018	Jan. 31, 2018	Oct. 31, 2017	Jul. 31, 2017	Apr. 30, 2017	Jan. 31, 2019	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total stockholders' equity	$ 1,170,383	$ 1,260,804				$ 1,132,336				$ 1,260,804	$ 1,132,336	$ 1,015,040	$ 1,068,164
Revenue		330,230	$ 303,983	$ 306,327	$ 289,207	$ 318,731	$ 280,726	$ 274,777	$ 260,995	1,229,747	1,135,229	1,062,106
Cost of Revenue										449,213	$ 446,787	$ 422,629
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total stockholders' equity	38,047	$ 89,600								$ 89,600
Revenue	17,200
Deferred Costs	4,200
Cost of Revenue	2,900
Capitalized Contract Cost, Net	16,900
Deferred Income Taxes	$ 3,200