LONG-TERM DEBT - INTEREST EXPENSE (Details) - USD ($)
$ in Thousands
3 Months Ended
Apr. 30, 2018
Apr. 30, 2017
1.50% Convertible Senior Notes    
Debt Instrument    
Interest Expense at Coupon or Contractual Rate $ 1,500 $ 1,500
Amortization of Debt Discount 2,904 2,756
Amortization of Deferred Debt Issuance Costs 274 260
Total Interest Expense 4,678 4,516
Credit Agreements    
Debt Instrument    
Interest Expense at Coupon or Contractual Rate 3,866 3,719
Amortization of Debt Discount 16 15
Amortization of Deferred Debt Issuance Costs 378 541
Total Interest Expense 4,260 4,453
Interest rate swap | Credit Agreements    
Debt Instrument    
Impact of Interest Rate Swap $ 0 $ 178