FAIR VALUE (Fair Value by Balance Sheet Grouping) (Details) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Thousands | Apr. 30, 2016 | Jan. 31, 2016 |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Total assets | $ 489,826 | $ 641,805 |
Commercial paper [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents | 73,454 | 31,580 |
Money market funds [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents | 15,351 | 105,787 |
Certificates of deposit [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments | 3,000 | 7,000 |
Commercial paper [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments | 32,505 | 47,690 |
Corporate debt securities [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents | 5,466 | |
Short-term investments | 305,798 | 387,529 |
Foreign government securities [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments | 9,414 | 9,452 |
Variable-rate demand notes [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments | 215 | 215 |
Asset and mortgage-backed securities [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments | 15,961 | 20,987 |
Municipal bonds [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments | 18,243 | 13,804 |
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Total assets | 15,351 | 105,787 |
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Commercial paper [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents | 0 | 0 |
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Money market funds [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents | 15,351 | 105,787 |
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Certificates of deposit [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments | 0 | 0 |
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Commercial paper [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments | 0 | 0 |
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Corporate debt securities [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents | 0 | |
Short-term investments | 0 | 0 |
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Foreign government securities [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments | 0 | 0 |
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Variable-rate demand notes [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments | 0 | 0 |
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Asset and mortgage-backed securities [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments | 0 | 0 |
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Municipal bonds [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments | 0 | 0 |
Significant Other Observable Inputs (Level 2) [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Total assets | 464,056 | 525,920 |
Significant Other Observable Inputs (Level 2) [Member] | Commercial paper [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents | 73,454 | 31,580 |
Significant Other Observable Inputs (Level 2) [Member] | Money market funds [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents | 0 | 0 |
Significant Other Observable Inputs (Level 2) [Member] | Certificates of deposit [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments | 3,000 | 7,000 |
Significant Other Observable Inputs (Level 2) [Member] | Commercial paper [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments | 32,505 | 47,690 |
Significant Other Observable Inputs (Level 2) [Member] | Corporate debt securities [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents | 5,466 | |
Short-term investments | 305,798 | 387,529 |
Significant Other Observable Inputs (Level 2) [Member] | Foreign government securities [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments | 9,414 | 9,452 |
Significant Other Observable Inputs (Level 2) [Member] | Variable-rate demand notes [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments | 215 | 215 |
Significant Other Observable Inputs (Level 2) [Member] | Asset and mortgage-backed securities [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments | 15,961 | 20,987 |
Significant Other Observable Inputs (Level 2) [Member] | Municipal bonds [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments | 18,243 | 13,804 |
Significant Unobservable Inputs (Level 3) [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Total assets | 10,419 | 10,098 |
Significant Unobservable Inputs (Level 3) [Member] | Commercial paper [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents | 0 | 0 |
Significant Unobservable Inputs (Level 3) [Member] | Money market funds [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents | 0 | 0 |
Significant Unobservable Inputs (Level 3) [Member] | Certificates of deposit [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments | 0 | 0 |
Significant Unobservable Inputs (Level 3) [Member] | Commercial paper [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments | 0 | 0 |
Significant Unobservable Inputs (Level 3) [Member] | Corporate debt securities [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents | 0 | |
Short-term investments | 0 | 0 |
Significant Unobservable Inputs (Level 3) [Member] | Foreign government securities [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments | 0 | 0 |
Significant Unobservable Inputs (Level 3) [Member] | Variable-rate demand notes [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments | 0 | 0 |
Significant Unobservable Inputs (Level 3) [Member] | Asset and mortgage-backed securities [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments | 0 | 0 |
Significant Unobservable Inputs (Level 3) [Member] | Municipal bonds [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments | 0 | 0 |
Contingent Purchase Consideration [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments | 10,419 | 10,098 |
Contingent Purchase Consideration [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments | 0 | 0 |
Contingent Purchase Consideration [Member] | Significant Other Observable Inputs (Level 2) [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments | 0 | 0 |
Contingent Purchase Consideration [Member] | Significant Unobservable Inputs (Level 3) [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments | $ 10,419 | $ 10,098 |