Marketable Securities Available-For-Sale - Classified as Available-for-Sale (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 27,763	$ 51,007
Gross Unrealized Gain	24	140
Gross Unrealized Loss	(16)	(138)
Fair Value	27,771	51,009
Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	16,404	25,608
Gross Unrealized Gain	9	122
Gross Unrealized Loss	(6)	(73)
Fair Value	16,407	25,657
Asset-backed securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	4,857	12,424
Gross Unrealized Gain	1	0
Gross Unrealized Loss	(3)	(31)
Fair Value	4,855	12,393
Government and agency securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,517	5,705
Gross Unrealized Gain	5	16
Gross Unrealized Loss	0	(9)
Fair Value	3,522	5,712
Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,195	4,800
Gross Unrealized Gain	8	2
Gross Unrealized Loss	(7)	(23)
Fair Value	2,196	4,779
Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	790	2,470
Gross Unrealized Gain	1	0
Gross Unrealized Loss	0	(2)
Fair Value	$ 791	$ 2,468