Basis of Presentation - Additional Information (Detail) - USD ($) $ in Thousands, shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Maximum period for cash and highly liquid securities with original maturities			90 days or less
Minimum period for marketable securities classified as available-for-sale with original maturities			More than 90 days
Amount of letter of credit, description			The Company is required to maintain a letter of credit securing an amount equal to twelve months of the current monthly installment of base rent for the term of its primary facilities lease, which ends in August 2017.
Restricted cash	$ 3,246		$ 3,246		$ 3,182
Common stock equivalents excluded from the calculation of diluted net income per share	0.1	0.4	0.4	0.5
Expected forfeiture rate of equity based compensation			8.75%	11.20%