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)

v3.5.0.2
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, 2016
Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost $ 141,868 $ 135,201
Fair Value 142,656 134,255
Short-term investments [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 48,354 79,943
Gross Unrealized Gains 24 0
Gross Unrealized Losses (1) (83)
Fair Value 48,377 79,860
Short-term investments [Member] | U.S. Treasuries [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 24,864 62,343
Gross Unrealized Gains 15 0
Gross Unrealized Losses (1) (71)
Fair Value 24,878 62,272
Short-term investments [Member] | U.S. Government Sponsored Entities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 11,508 17,571
Gross Unrealized Gains 5 0
Gross Unrealized Losses 0 (12)
Fair Value 11,513 17,559
Short-term investments [Member] | Corporate debt securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 11,982 0
Gross Unrealized Gains 4 0
Gross Unrealized Losses 0 0
Fair Value 11,986 0
Short-term investments [Member] | Asset-backed securities and other [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 0 29
Gross Unrealized Gains 0 0
Gross Unrealized Losses 0 0
Fair Value 0 29
Long-term marketable securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 93,514 55,258
Gross Unrealized Gains 844 5
Gross Unrealized Losses (79) (868)
Fair Value 94,279 54,395
Long-term marketable securities [Member] | U.S. Treasuries [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 50,535 15,283
Gross Unrealized Gains 172 0
Gross Unrealized Losses (9) (112)
Fair Value 50,698 15,171
Long-term marketable securities [Member] | U.S. Government Sponsored Entities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 15,989 12,107
Gross Unrealized Gains 25 0
Gross Unrealized Losses 0 (85)
Fair Value 16,014 12,022
Long-term marketable securities [Member] | Corporate debt securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 18,261 17,219
Gross Unrealized Gains 529 5
Gross Unrealized Losses (21) (519)
Fair Value 18,769 16,705
Long-term marketable securities [Member] | Asset-backed securities and other [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 8,729 10,649
Gross Unrealized Gains 118 0
Gross Unrealized Losses (49) (152)
Fair Value $ 8,798 $ 10,497