RECENTLY ISSUED ACCOUNTING PRONOUNCEMENTS (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2015
Recently issued accounting pronouncements
Income tax expense (benefit)	$ 37,106	$ 25,302	$ 20,912
Deferred income tax liabilities, noncurrent	954	224
Accounting Standards Update ('ASU') 2016-09 - Reduction in income tax expense: Improvements to Employee Share-Based Payment Accounting
Recently issued accounting pronouncements
Income tax expense (benefit)	$ 5,000
Accounting Standards Update ("ASU") 2015-17 - Income Taxes: Balance Sheet Classification of Deferred Taxes
Recently issued accounting pronouncements
Deferred income tax liabilities, noncurrent		$ 1,100