Annual report pursuant to Section 13 and 15(d)

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

v3.3.1.900
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
Dec. 31, 2015
Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost $ 135,201 $ 14,712
Fair Value 134,255 14,752
Short-term investments [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 79,943  
Gross Unrealized Losses (83)  
Fair Value 79,860  
Short-term investments [Member] | U.S. Treasuries [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 62,343  
Gross Unrealized Losses (71)  
Fair Value 62,272  
Short-term investments [Member] | U.S. Government Sponsored Entities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 17,571  
Gross Unrealized Losses (12)  
Fair Value 17,559  
Short-term investments [Member] | Asset-backed securities and other [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 29  
Fair Value 29  
Long-term marketable securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 55,258 14,712
Gross Unrealized Gains 5 59
Gross Unrealized Losses (868) (19)
Fair Value 54,395 14,752
Long-term marketable securities [Member] | U.S. Treasuries [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 15,283 2,974
Gross Unrealized Gains   7
Gross Unrealized Losses (112)  
Fair Value 15,171 2,981
Long-term marketable securities [Member] | U.S. Government Sponsored Entities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 12,107 2,019
Gross Unrealized Losses (85) (3)
Fair Value 12,022 2,016
Long-term marketable securities [Member] | Corporate debt securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 17,219 7,442
Gross Unrealized Gains 5 48
Gross Unrealized Losses (519) (12)
Fair Value 16,705 7,478
Long-term marketable securities [Member] | Asset-backed securities and other [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 10,649 2,277
Gross Unrealized Gains   4
Gross Unrealized Losses (152) (4)
Fair Value $ 10,497 $ 2,277