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STOCK-BASED COMPENSATION - Additional Information (Details) - USD ($) $ in Thousands, shares in Millions	12 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award
Intrinsic value of outstanding stock options	$ 6,300
Compensation expense	4,651	$ 2,344	$ 2,374
Unrecognized compensation cost	$ 2,400
Estimated expected life	P5Y6M
Estimated expected life simplified method	P3Y3M18D
Period used for calculations	5 years
Company's expense for defined contribution savings plans	$ 2,800	1,900	1,500
Stock Options Plans
Share-based Compensation Arrangement by Share-based Payment Award
Number of shares of common stock reserved for issuance	1.0
Compensation expense	$ 4,700	2,300	2,400
Compensation expense recognize, period	3 years
Intrinsic value of the stock options exercised	$ 3,600	$ 18,400	$ 2,100
Method used for fair value assumption	Black-Scholes option pricing model	Black-Scholes option pricing model	Black-Scholes option pricing model
Risk-free interest rate, minimum	1.50%	1.30%	1.00%
Risk-free interest rate, maximum	2.00%	1.90%	1.70%
Volatility rate, minimum	36.00%	33.30%	33.90%
Volatility rate, maximum	38.30%	35.00%	35.30%
Stock Options Plans | Stock Plan
Share-based Compensation Arrangement by Share-based Payment Award
Number of shares of common stock available for award	0.2
ISOs | Stock Plan
Share-based Compensation Arrangement by Share-based Payment Award
Incentive stock option award maximum expiration period	10 years
NSOs | Stock Plan
Share-based Compensation Arrangement by Share-based Payment Award
Incentive stock option award maximum expiration period	10 years
NSOs | Stock Plan | Minimum
Share-based Compensation Arrangement by Share-based Payment Award
Period to become exercisable	1 year
NSOs | Stock Plan | Maximum
Share-based Compensation Arrangement by Share-based Payment Award
Period to become exercisable	3 years

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The period of monthly closing prices used for the estimated measure of the maximum percentage by which a share price is expected to fluctuate during a period. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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Aggregate number of common shares reserved for future issuance.

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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Unrecognized cost of unvested options awarded to employees as compensation.

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Description of the expected term under the specified contract (or assumed time period) the instrument will be outstanding before being exercised, placed into service or terminated, the reason and justification for its use, and the periods for which the method was used.

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Discloses use of the simplified method to calculate the expected term that stock option awards under the specified plan will exist before being exercised or terminated, the reason and justification for its use, and the periods for which the method was used if it was not used in all periods presented.

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The estimated measure of the maximum percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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For each plan, identification of the award pricing model or other valuation method used in calculating the weighted average fair values disclosed. The model is also used to calculate the compensation expense that is shown within the balance sheet, income statement, and cash flow. Examples of valuation techniques are lattice models (binomial model), closed-form models (Black-Scholes-Merton formula), and a Monte Carlo simulation technique. Fair value is the amount at which an asset or liability could be bought or incurred or sold or settled in a current transaction between willing parties, that is, other than in a forced or liquidation sale. May include disclosures about the assumptions underlying application of the method selected.

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The maximum risk-free interest rate assumption that is used in valuing an option on its own shares.

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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The noncash expense that accounts for the value of stock or unit options distributed to employees as compensation.

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