REVENUE RECOGNITION REVENUE RECOGNITION - CURRENT PERIOD BALANCE SHEET - IMPACT OF ADOPTION (Details) - USD ($)
$ in Thousands
Apr. 30, 2018
Feb. 01, 2018
Jan. 31, 2018
Apr. 30, 2017
Jan. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]          
Accounts receivable, net $ 303,108 $ 350,006 $ 296,324    
Contract assets 87,963 69,217 0    
Deferred cost of revenue 8,501 8,152 6,096    
Prepaid expenses and other current assets 77,058 81,261 82,090    
Long-term deferred cost of revenue 4,478 4,997 2,804    
Other assets 93,486 66,949 82,915    
Accrued expenses and other current liabilities 193,828 174,203 224,765    
Contract liabilities 332,139 335,624 196,107    
Long-term contract liabilities 28,354 31,037 24,519    
Other liabilities 135,799   149,770    
Total stockholders' equity 1,163,271 1,170,383 $ 1,132,336 $ 1,023,072 $ 1,015,040
Calculated under Revenue Guidance in Effect before Topic 606 | Accounting Standards Update 2014-09          
New Accounting Pronouncements or Change in Accounting Principle [Line Items]          
Accounts receivable, net 298,605        
Contract assets 0        
Deferred cost of revenue 9,238        
Prepaid expenses and other current assets 79,059        
Long-term deferred cost of revenue 2,137        
Other assets 77,056        
Accrued expenses and other current liabilities 234,568        
Contract liabilities 244,702        
Long-term contract liabilities 24,244        
Other liabilities 134,844        
Total stockholders' equity 1,106,534        
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09          
New Accounting Pronouncements or Change in Accounting Principle [Line Items]          
Accounts receivable, net 4,503 53,682      
Contract assets 87,963 69,217      
Deferred cost of revenue (737) 2,056      
Prepaid expenses and other current assets (2,001) (829)      
Long-term deferred cost of revenue 2,341 2,193      
Other assets 16,430 14,912      
Accrued expenses and other current liabilities (40,740) (46,062)      
Contract liabilities 87,437 139,517      
Long-term contract liabilities 4,110 6,518      
Other liabilities 955        
Total stockholders' equity $ 56,737 $ 38,047