Stock Plans - Weighted Average for Key Assumptions in Determining Fair Value of Options Granted (Detail)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Expected volatility		70.60%	68.20%
Weighted-average expected volatility		70.60%	68.20%
Expected dividends
Expected term (in years)		5 years 2 months 12 days	5 years 1 month 6 days
Risk-free rate		0.90%	2.10%