Future Payments (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Debt Instrument [Line Items]
2013	$ 1,183
2014	3,995
2015	3,699
2016	3,403
Total minimum payments	12,280
Less amount representing interest	(2,280)
Notes payable, gross	10,000
Discount on notes payable	(186)
Accretion of the final exit fee payment	12
Long-term notes payable	$ 9,826