XML 52 R40.htm IDEA: XBRL DOCUMENT v2.4.0.8
Marketable Securities - Additional Information (Detail) (USD $)
In Thousands, unless otherwise specified
 12 Months Ended 3 Months Ended 12 Months Ended
Jan. 31, 2014
Securities
Jan. 31, 2013
Securities
Jan. 31, 2012
Jan. 31, 2014
Long Term Investments
Jan. 31, 2013
Long Term Investments
Apr. 30, 2013
Auction Rate Securities
Jan. 31, 2013
Auction Rate Securities
Jan. 31, 2013
Auction Rate Securities
Long Term Investments
Jan. 31, 2014
Other Expense Income Net
Jan. 31, 2013
Other Expense Income Net
Jan. 31, 2012
Other Expense Income Net
Schedule of Available-for-sale Securities [Line Items]                      
Proceeds from sale and maturities of available-for-sale securities $ 451,866 $ 207,576 $ 414,769                
Net realized gain (loss)                 (101) 248 1,171
Amortization of discounts and premiums, net 10,932 5,276 7,373                
Number of securities with unrealized loss positions 219 342                  
Proceeds from sale of available-for-sale securities           4,580          
Amortized cost of available-for-sale securities 647,483 378,393   365,809 150,107     4,925      
Estimated fair value of available-for-sale securities 648,235 378,071   366,422 149,585   4,330 4,330      
12 Months or Greater, Unrealized Losses   $ 595         $ 595