XML 17 R24.htm IDEA: XBRL DOCUMENT v2.4.0.8
Amortized Cost, Gross Unrealized Gains (Losses) and Fair Value of Available-For-Sale Securities (Detail) (USD $)
In Thousands, unless otherwise specified
Oct. 31, 2013
Jan. 31, 2013
Oct. 31, 2012
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost $ 530,169 $ 378,393 $ 240,083
Unrealized Gains 765 438 442
Unrealized (Losses) (187) (760) (693)
Fair Value 530,747 378,071 239,832
Short-term Investments
      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 227,439 228,286 145,848
Unrealized Gains 138 242 230
Unrealized (Losses) (30) (42) (13)
Fair Value 227,547 228,486 146,065
Long Term Investments
      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 302,730 150,107 94,235
Unrealized Gains 627 196 212
Unrealized (Losses) (157) (718) (680)
Fair Value 303,200 149,585 93,767
Corporate Bonds
      
Schedule of Available-for-sale Securities [Line Items]      
Fair Value 234,041 152,775 111,662
Corporate Bonds | Short-term Investments
      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 77,806 88,432 64,975
Unrealized Gains 37 106 89
Unrealized (Losses) (25) (23) (7)
Fair Value 77,818 88,515 65,057
Corporate Bonds | Long Term Investments
      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 156,170 64,219 46,507
Unrealized Gains 197 102 155
Unrealized (Losses) (144) (61) (57)
Fair Value 156,223 64,260 46,605
Municipal And Pre-Refunded Municipal Bonds
      
Schedule of Available-for-sale Securities [Line Items]      
Fair Value 207,397 116,364 51,505
Municipal And Pre-Refunded Municipal Bonds | Short-term Investments
      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 84,662 63,355 29,937
Unrealized Gains 71 85 98
Unrealized (Losses) (3) (17) (6)
Fair Value 84,730 63,423 30,029
Municipal And Pre-Refunded Municipal Bonds | Long Term Investments
      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 122,356 52,925 21,456
Unrealized Gains 324 76 47
Unrealized (Losses) (13) (60) (27)
Fair Value 122,667 52,941 21,476
Certificates of Deposit
      
Schedule of Available-for-sale Securities [Line Items]      
Fair Value 28,752 43,235 30,630
Certificates of Deposit | Short-term Investments
      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 26,733 40,870 28,676
Unrealized Gains 17 25 28
Fair Value 26,750 40,895 28,704
Certificates of Deposit | Long Term Investments
      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 2,001 2,340 1,925
Unrealized Gains 1   1
Fair Value 2,002 2,340 1,926
Commercial Paper
      
Schedule of Available-for-sale Securities [Line Items]      
Fair Value 28,167 10,781 8,189
Commercial Paper | Short-term Investments
      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 28,159 10,775 8,178
Unrealized Gains 10 8 11
Unrealized (Losses) (2) (2)  
Fair Value 28,167 10,781 8,189
US Treasury Bill Securities
      
Schedule of Available-for-sale Securities [Line Items]      
Fair Value 22,274 41,105 28,803
US Treasury Bill Securities | Short-term Investments
      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 10,079 21,354 10,582
Unrealized Gains 3 14 4
Fair Value 10,082 21,368 10,586
US Treasury Bill Securities | Long Term Investments
      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 12,183 19,724 18,211
Unrealized Gains 9 13 7
Unrealized (Losses)     (1)
Fair Value 12,192 19,737 18,217
US Government Corporations and Agencies Securities
      
Schedule of Available-for-sale Securities [Line Items]      
Fair Value 8,788 9,481 4,713
US Government Corporations and Agencies Securities | Short-term Investments
      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost   3,500 3,500
Unrealized Gains   4  
Fair Value   3,504 3,500
US Government Corporations and Agencies Securities | Long Term Investments
      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 8,784 5,974 1,211
Unrealized Gains 4 5 2
Unrealized (Losses)   (2)  
Fair Value 8,788 5,977 1,213
Mutual funds, held in rabbi trust
      
Schedule of Available-for-sale Securities [Line Items]      
Fair Value 1,328    
Mutual funds, held in rabbi trust | Long Term Investments
      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 1,236    
Unrealized Gains 92    
Fair Value 1,328    
Auction Rate Securities
      
Schedule of Available-for-sale Securities [Line Items]      
Fair Value   4,330 4,330
Auction Rate Securities | Long Term Investments
      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost   4,925 4,925
Unrealized (Losses)   (595) (595)
Fair Value   $ 4,330 $ 4,330