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 $)
In Thousands, unless otherwise specified
Sep. 30, 2014
Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost $ 60,473 $ 60,293
Available-for-sale Securities Gross Unrealized Gain Accumulated in Investments 19 27
Available-for-sale Securities Gross Unrealized Loss Accumulated in Investments 27 9
Fair Value 60,465 60,311
Cash and cash equivalents [Member]
    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 603 406
Available-for-sale Securities Gross Unrealized Gain Accumulated in Investments 0 0
Available-for-sale Securities Gross Unrealized Loss Accumulated in Investments 0 0
Fair Value 603 406
Investments [Member]
    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 59,870 59,887
Available-for-sale Securities Gross Unrealized Gain Accumulated in Investments 19 27
Available-for-sale Securities Gross Unrealized Loss Accumulated in Investments 27 9
Fair Value 59,862 59,905
US Government Agencies Debt Securities [Member]
    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 23,419 26,532
Available-for-sale Securities Gross Unrealized Gain Accumulated in Investments 13 10
Available-for-sale Securities Gross Unrealized Loss Accumulated in Investments 0 5
Fair Value 23,432 26,537
Corporate debt securities [Member]
    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 36,451 33,355
Available-for-sale Securities Gross Unrealized Gain Accumulated in Investments 6 17
Available-for-sale Securities Gross Unrealized Loss Accumulated in Investments 27 4
Fair Value 36,430 33,368
Money market funds [Member]
    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 603 406
Available-for-sale Securities Gross Unrealized Gain Accumulated in Investments 0 0
Available-for-sale Securities Gross Unrealized Loss Accumulated in Investments 0 0
Fair Value $ 603 $ 406