FAIR VALUE (Fair Value by Balance Sheet Grouping) (Details) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Thousands | Oct. 31, 2015 | Jan. 31, 2015 |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Total assets | $ 664,294 | $ 713,826 |
Commercial paper [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents | 106,065 | 48,210 |
Money market funds [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents | 13,914 | 100,872 |
Certificates of deposit [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments | 15,400 | 27,400 |
Commercial paper [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments | 58,738 | 85,062 |
Corporate debt securities [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents | 4,279 | |
Short-term investments | 409,874 | 416,333 |
Foreign government securities [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments | 10,815 | 10,849 |
Variable-rate demand notes [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments | 215 | 285 |
Asset and mortgage-backed securities [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments | 21,883 | 18,861 |
Municipal bonds [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments | 13,079 | 5,954 |
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 | 13,914 | 100,872 |
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 | 13,914 | 100,872 |
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 | 640,348 | 612,954 |
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 | 106,065 | 48,210 |
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 | 15,400 | 27,400 |
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 | 58,738 | 85,062 |
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 | 4,279 | |
Short-term investments | 409,874 | 416,333 |
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 | 10,815 | 10,849 |
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 | 285 |
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 | 21,883 | 18,861 |
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 | 13,079 | 5,954 |
Significant Unobservable Inputs (Level 3) [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Total assets | 10,032 | 0 |
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 | 10,032 | |
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 | |
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 | |
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 | $ 10,032 | |