Marketable Securities, Available for Sale - Summary of Available-for-Sale Marketable Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 19,859	$ 23,511
Unrealized Gain	5	0
Unrealized Loss	0	12
Market Value	19,864	23,499
U.S. treasuries [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	5,030	5,558
Unrealized Gain	5	0
Unrealized Loss	0	1
Market Value	5,035	5,557
Government-sponsored enterprise securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,000	7,499
Unrealized Gain	0	0
Unrealized Loss	0	6
Market Value	2,000	7,493
Corporate bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,005	2,025
Unrealized Gain	0	0
Unrealized Loss	0	5
Market Value	2,005	2,020
Certificates of deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	10,824	8,429
Unrealized Gain	0	0
Unrealized Loss	0	0
Market Value	$ 10,824	$ 8,429