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
Jun. 30, 2016
Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost $ 145,072 $ 135,201
Fair Value 145,953 134,255
Short-term investments [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 81,726 79,943
Gross Unrealized Gains 49 0
Gross Unrealized Losses 0 (83)
Fair Value 81,775 79,860
Short-term investments [Member] | U.S. Treasuries [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 53,278 62,343
Gross Unrealized Gains 35 0
Gross Unrealized Losses 0 (71)
Fair Value 53,313 62,272
Short-term investments [Member] | U.S. Government Sponsored Entities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 8,509 17,571
Gross Unrealized Gains 7 0
Gross Unrealized Losses 0 (12)
Fair Value 8,516 17,559
Short-term investments [Member] | Corporate debt securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 19,939 29
Gross Unrealized Gains 7 0
Gross Unrealized Losses 0 0
Fair Value 19,946 29
Long-term marketable securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 63,346 55,258
Gross Unrealized Gains 929 5
Gross Unrealized Losses (97) (868)
Fair Value 64,178 54,395
Long-term marketable securities [Member] | U.S. Treasuries [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 21,176 15,283
Gross Unrealized Gains 250 0
Gross Unrealized Losses 0 (112)
Fair Value 21,426 15,171
Long-term marketable securities [Member] | U.S. Government Sponsored Entities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 15,919 12,107
Gross Unrealized Gains 48 0
Gross Unrealized Losses 0 (85)
Fair Value 15,967 12,022
Long-term marketable securities [Member] | Corporate debt securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 16,412 17,219
Gross Unrealized Gains 503 5
Gross Unrealized Losses (39) (519)
Fair Value 16,876 16,705
Long-term marketable securities [Member] | Asset-backed securities and other [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 9,839 10,649
Gross Unrealized Gains 128 0
Gross Unrealized Losses (58) (152)
Fair Value $ 9,909 $ 10,497