Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Accounting Policies [Abstract]
Impairment of investments			$ 0
Based on these sales prices reduced inventory and increased cost of goods sold			421,000		1,500,000
Reduced inventory and increased costs of goods sold	11,000		266,000		719,000
Revenue recorded from government contract	882,000	422,000	1,091,000	422,000
Period of contract	3 years
Total value of the contract	4,700,000		4,700,000
Value of contract recorded	$ 2,300,000