Fair Value Measurements - Available-for-Sale Securities Measured at Fair Value (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale securities	$ 729	$ 3,915
Mutual funds [Member]
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale securities	729	2,216
Commercial paper [Member]
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale securities		1,699
Level 2 [Member]
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale securities	729	3,915
Level 2 [Member] | Mutual funds [Member]
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale securities	$ 729	2,216
Level 2 [Member] | Commercial paper [Member]
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale securities		$ 1,699