Marketable Securities, Available for Sale - Summary of Available-for-Sale Marketable Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 28,988	$ 23,266
Unrealized Gain	2	0
Unrealized Loss	0	8
Market Value	28,990	23,258
U.S. treasuries [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	18,783	7,027
Unrealized Gain	2	0
Unrealized Loss	0	8
Market Value	18,785	7,019
Certificates of deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	10,205	15,239
Unrealized Gain	0	0
Unrealized Loss	0	0
Market Value	$ 10,205	15,239
Corporate bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		1,000
Unrealized Gain		0
Unrealized Loss		0
Market Value		$ 1,000