Quarterly report pursuant to Section 13 or 15(d)

Financial Instruments - Additional Information (Detail)

v2.4.0.6
Financial Instruments - Additional Information (Detail) (USD $)
9 Months Ended
Sep. 30, 2012
Instruments
Dec. 31, 2011
Debt Instrument [Line Items]    
Number of corporate debt securities 7  
Fair value of debt $ 13,090  
Gross unrealized losses 4,000 30,000
Transfer of securities, Level 1 0  
Transfer of securities, Level 2 0  
Transfer of securities, Level 3 $ 0  
Maximum [Member]
   
Debt Instrument [Line Items]    
Period of unrealized loss position 12 months  
Due date of company's long term available for sale securities 2 years  
Minimum [Member]
   
Debt Instrument [Line Items]    
Due date of company's long term available for sale securities 1 year