SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - IMPACT OF ASU NO. 2016-16 (Details) - USD ($) $ in Thousands	Jan. 31, 2018	Feb. 01, 2017	Jan. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accumulated deficit	$ (238,312)		$ (230,816)
Prepaid expenses and other current assets	82,090		64,561
Other assets	$ 52,037		$ 76,620
Accounting Standards Update 2016-16
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accumulated deficit		$ (900)
Prepaid expenses and other current assets		(1,300)
Other assets		$ 400