Annual report pursuant to Section 13 and 15(d)

Financial Instruments - Composition of Financial Instruments (Detail)

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Financial Instruments - Composition of Financial Instruments (Detail) (USD $)
Dec. 31, 2013
Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost $ 60,293,000 $ 60,084,000
Gross unrealized gains 27,000 9,000
Gross unrealized losses (9,000) (4,000)
Fair Value 60,311,000 60,089,000
Cash and cash equivalents [Member]
    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 406,000 4,643,000
Gross unrealized gains 0 0
Gross unrealized losses 0 0
Fair Value 406,000 4,643,000
Investments [Member]
    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 59,887,000 55,441,000
Gross unrealized gains 27,000 9,000
Gross unrealized losses (9,000) (4,000)
Fair Value 59,905,000 55,446,000
US Government Agencies Debt Securities [Member]
    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 26,532,000 6,000,000
Gross unrealized gains 10,000 3,000
Gross unrealized losses (5,000) 0
Fair Value 26,537,000 6,003,000
Corporate debt securities [Member]
    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 33,355,000 49,441,000
Gross unrealized gains 17,000 6,000
Gross unrealized losses (4,000) (4,000)
Fair Value 33,368,000 49,443,000
Money market funds [Member]
    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 406,000 4,643,000
Gross unrealized gains 0 0
Gross unrealized losses 0 0
Fair Value $ 406,000 $ 4,643,000