Financial Instruments - Carrying Value and Estimated Fair Value of Financial Instruments (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014	Dec. 31, 2013
Fair Value Disclosures [Abstract]
Cash and cash equivalents, Carrying amount	$ 47,904	$ 45,570	$ 41,862	$ 38,753
Accounts receivable, net, Carrying amount	11,605	8,747
Accounts payable, Carrying amount	3,064	3,850
Cash and cash equivalents, Fair value	47,904	45,570
Accounts receivable, net, Fair value	11,605	8,747
Accounts payable, Fair value	$ 3,064	$ 3,850