Quarterly report pursuant to Section 13 or 15(d)

Financial Instruments - Composition of Financial Instruments (Detail)

v3.2.0.727
Financial Instruments - Composition of Financial Instruments (Detail) - USD ($)
$ in Thousands
Jun. 30, 2015
Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost $ 30,780 $ 60,555
Gross Unrealized Gains 1 8
Gross Unrealized Losses (16) (50)
Fair Value 30,765 60,513
Less amounts included in cash and cash equivalents [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 5,421 1,858
Gross Unrealized Gains 0 0
Gross Unrealized Losses 0 0
Fair Value 5,421 1,858
Investments [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 25,359 58,697
Gross Unrealized Gains 1 8
Gross Unrealized Losses (16) (50)
Fair Value 25,344 58,655
Government debt securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 8,898 27,154
Gross Unrealized Gains 1 5
Gross Unrealized Losses 0 (8)
Fair Value 8,899 27,151
Corporate debt securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 16,461 31,543
Gross Unrealized Gains 0 3
Gross Unrealized Losses (16) (42)
Fair Value 16,445 31,504
Money market funds [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 5,421 1,858
Gross Unrealized Gains 0 0
Gross Unrealized Losses 0 0
Fair Value $ 5,421 $ 1,858