STOCK-BASED COMPENSATION STOCK-BASED COMPENSATION - RESTRICTED STOCK UNITS (Details) $ / shares in Units, $ in Millions	6 Months Ended
	Jul. 31, 2018 USD ($) $ / shares shares
RSUs
Summary of award activity
Beginning balance (in shares)	2,808,000
Granted (in shares)	1,527,000
Released (in shares)	(1,074,000)
Forfeited (in shares)	(184,000)
Ending balance (in shares)	3,077,000
Weighted-Average Grant-Date Fair Value
Beginning balance (in dollars per share) | $ / shares	$ 41.18
Granted (in dollars per share) | $ / shares	42.32
Released (in dollars per share) | $ / shares	43.90
Forfeited (in dollars per share) | $ / shares	41.13
Ending balance (in dollars per share) | $ / shares	$ 40.84
Additional disclosures
Unrecognized compensation expense | $	$ 84.9
Remaining weighted-average vesting period over which expense is expected to be recognized (in years)	2 years
RSUs, Excluding PSUs
Summary of award activity
Granted (in shares)	1,353,000