Quarterly report pursuant to Section 13 or 15(d)

Investments in Marketable Securities - Schedule of Amortized Cost and Fair Value of Marketable Securities, Available-for-Sale, by Type of Security (Detail)

v3.3.0.814
Investments in Marketable Securities - Schedule of Amortized Cost and Fair Value of Marketable Securities, Available-for-Sale, by Type of Security (Detail) - USD ($)
$ in Thousands
Sep. 30, 2015
Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost $ 135,136 $ 14,712
Fair Value 134,768 14,752
Short-term investments [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 89,731  
Gross Unrealized Gains 34  
Gross Unrealized Losses (1)  
Fair Value 89,764  
Short-term investments [Member] | U.S. Treasuries [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 70,497  
Gross Unrealized Gains 31  
Fair Value 70,528  
Short-term investments [Member] | U.S. Government Sponsored Entities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 19,110  
Gross Unrealized Gains 3  
Gross Unrealized Losses (1)  
Fair Value 19,112  
Short-term investments [Member] | Asset-backed securities and other [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 124  
Fair Value 124  
Long-term marketable securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 45,405 14,712
Gross Unrealized Gains 79 59
Gross Unrealized Losses (480) (19)
Fair Value 45,004 14,752
Long-term marketable securities [Member] | U.S. Treasuries [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 6,110 2,974
Gross Unrealized Gains 23 7
Gross Unrealized Losses (26)  
Fair Value 6,107 2,981
Long-term marketable securities [Member] | U.S. Government Sponsored Entities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 11,750 2,019
Gross Unrealized Gains 5  
Gross Unrealized Losses (13) (3)
Fair Value 11,742 2,016
Long-term marketable securities [Member] | Corporate debt securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 17,217 7,442
Gross Unrealized Gains 18 48
Gross Unrealized Losses (408) (12)
Fair Value 16,827 7,478
Long-term marketable securities [Member] | Asset-backed securities and other [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 10,328 2,277
Gross Unrealized Gains 33 4
Gross Unrealized Losses (33) (4)
Fair Value $ 10,328 $ 2,277