Cash and Cash Equivalents - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Jul. 25, 2012	Mar. 25, 2012
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents, money market accounts	$ 24,500	$ 7,000,000
Percentage of interest recognized from money market fund	0.01%	0.01%
Interest income from money market fund	280	932
Convertible secured promissory notes, principal amount			4,085,000
Convertible secured promissory notes, proceeds amount required to be maintained in an account subject to deposit account control agreement				$ 1,000,000