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
Jun. 30, 2014
Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost $ 60,454 $ 60,293
Available-for-sale Securities Gross Unrealized Gain Accumulated in Investments 27 27
Available-for-sale Securities Gross Unrealized Loss Accumulated in Investments 13 9
Fair Value 60,468 60,311
Cash and cash equivalents [Member]
    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 208 406
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 208 406
Investments [Member]
    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 60,246 59,887
Available-for-sale Securities Gross Unrealized Gain Accumulated in Investments 27 27
Available-for-sale Securities Gross Unrealized Loss Accumulated in Investments 13 9
Fair Value 60,260 59,905
US Government Agencies Debt Securities [Member]
    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 23,457 26,532
Available-for-sale Securities Gross Unrealized Gain Accumulated in Investments 11 10
Available-for-sale Securities Gross Unrealized Loss Accumulated in Investments 4 5
Fair Value 23,464 26,537
Corporate debt securities [Member]
    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 36,789 33,355
Available-for-sale Securities Gross Unrealized Gain Accumulated in Investments 16 17
Available-for-sale Securities Gross Unrealized Loss Accumulated in Investments 9 4
Fair Value 36,796 33,368
Money market funds [Member]
    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 208 406
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 $ 208 $ 406