Quarterly report pursuant to Section 13 or 15(d)

Financial Instruments - Composition of Financial Instruments (Detail)

v2.4.0.6
Financial Instruments - Composition of Financial Instruments (Detail) (USD $)
Mar. 31, 2013
Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost $ 60,118,000 $ 60,084,000
Gross unrealized gains 9,000 9,000
Gross unrealized losses (16,000) (4,000)
Fair Value 60,111,000 60,089,000
Cash and cash equivalents [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 28,000 4,643,000
Gross unrealized gains 0 0
Gross unrealized losses 0 0
Fair Value 28,000 4,643,000
Investments [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 60,090,000 55,441,000
Gross unrealized gains 9,000 9,000
Gross unrealized losses (16,000) (4,000)
Fair Value 60,083,000 55,446,000
US Government Agencies Debt Securities [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 13,273,000 6,000,000
Gross unrealized gains 4,000 3,000
Gross unrealized losses (1,000) 0
Fair Value 13,276,000 6,003,000
Corporate debt securities [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 46,817,000 49,441,000
Gross unrealized gains 5,000 6,000
Gross unrealized losses (15,000) (4,000)
Fair Value 46,807,000 49,443,000
Money market funds [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 28,000 4,643,000
Gross unrealized gains 0 0
Gross unrealized losses 0 0
Fair Value $ 28,000 $ 4,643,000