STOCK-BASED COMPENSATION - Additional Information (Details) - USD ($)	1 Months Ended	12 Months Ended
	Jun. 30, 2013	Jan. 31, 2016	Jan. 31, 2015	Jan. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award
Intrinsic value of the stock options exercised		$ 2,067,000	$ 5,708,000	$ 3,158,000
Intrinsic value of outstanding stock options		3,981,000
Intrinsic value of exercisable stock options		5,354,000
Compensation expense		2,374,000	2,017,000	1,536,000
Unrecognized compensation cost		$ 1,370,000
Period used for calculations		5 years
Company's expense for defined contribution savings plans		$ 1,462,000	1,069,000	677,000
Stock Options Plans
Share-based Compensation Arrangement by Share-based Payment Award
Number of shares of common stock reserved for issuance		1,773,900
Compensation expense		$ 2,374,000	$ 2,017,000	$ 1,536,000
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		1.00%	0.10%	0.70%
Risk-free interest rate, maximum		1.70%	1.60%	1.50%
Volatility rate, minimum		33.90%	29.90%	32.30%
Volatility rate, maximum		35.30%	34.40%	34.30%
Stock Options Plans | Stock Plan
Share-based Compensation Arrangement by Share-based Payment Award
Increase in number of shares of common stock reserved for issuance	750,000
Number of shares of common stock available for award		710,000
ISOs | Stock Plan
Share-based Compensation Arrangement by Share-based Payment Award
Period to become exercisable		1 year
ISOs | Stock Plan | Maximum
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
Period to become exercisable		1 year
NSOs | Stock Plan | Maximum
Share-based Compensation Arrangement by Share-based Payment Award
Incentive stock option award maximum expiration period		10 years