Summary of Available for Sale Securities (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Carrying Value	$ 31,427	$ 36,834
Net Unrealized Gain	(11)	7
Fair Value	31,416	36,841
Money market funds
Schedule of Available-for-sale Securities [Line Items]
Carrying Value	6,185	8,650
Net Unrealized Gain	0	0
Fair Value	6,185	8,650
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Carrying Value	21,813	23,165
Net Unrealized Gain	(11)	8
Fair Value	21,802	23,173
United States government agency securities
Schedule of Available-for-sale Securities [Line Items]
Carrying Value	3,429	5,019
Net Unrealized Gain	0	(1)
Fair Value	$ 3,429	$ 5,018