Quarterly report pursuant to Section 13 or 15(d)

Financial Instruments - Composition of Financial Instruments (Detail)

v2.4.0.8
Financial Instruments - Composition of Financial Instruments (Detail) (USD $)
Jun. 30, 2013
Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost $ 60,161,000 $ 60,084,000
Gross unrealized gains 3,000 9,000
Gross unrealized losses (43,000) (4,000)
Fair Value 60,121,000 60,089,000
Cash and cash equivalents [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 3,584,000 4,643,000
Gross unrealized gains 0 0
Gross unrealized losses 0 0
Fair Value 3,584,000 4,643,000
Investments [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 56,577,000 55,441,000
Gross unrealized gains 3,000 9,000
Gross unrealized losses (43,000) (4,000)
Fair Value 56,537,000 55,446,000
US Government Agencies Debt Securities [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 20,318,000 6,000,000
Gross unrealized gains 2,000 3,000
Gross unrealized losses (14,000) 0
Fair Value 20,306,000 6,003,000
Corporate debt securities [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 36,259,000 49,441,000
Gross unrealized gains 1,000 6,000
Gross unrealized losses (29,000) (4,000)
Fair Value 36,231,000 49,443,000
Money market funds [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 3,584,000 4,643,000
Gross unrealized gains 0 0
Gross unrealized losses 0 0
Fair Value $ 3,584,000 $ 4,643,000