Equity Incentive Plans - Employee Stock Purchase Plan - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Oct. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Feb. 29, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate limit of common stock		200,000,000	200,000,000
Company's incremental common stock shares reserved for issuance		1,700,000
ESPP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock initially reserved for issuance					300,000
Shares available for issuance under plan annual increase rate					1.00%
Company's incremental common stock shares reserved for issuance	250,000
Common stock issued to employees		134,579	149,788	49,912
Unrecognized compensation expenses		$ 0.1
Unrecognized compensation expense, weighted-average period		4 months 24 days
Shares available for issuance under the plan		134,449
ESPP [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for issuance under Plan annual increase					500,000
Aggregate limit of common stock					3,000,000