XML 14 R54.htm IDEA: XBRL DOCUMENT v3.3.1.900
Securities Available for Sale - Additional Information (Detail)
9 Months Ended
Oct. 31, 2015
USD ($)
Schedule of Available-for-sale Securities [Line Items]  
Impairment charges on available for sale security $ 0
Minimum [Member]  
Schedule of Available-for-sale Securities [Line Items]  
Original maturity of short-term investments 90 days
Anticipated maturity period 1 month
Maximum [Member]  
Schedule of Available-for-sale Securities [Line Items]  
Anticipated maturity period 27 months