State Research and Development Credit Exchange Receivable - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Accounts and Other Receivables [Line Items]
Estimated amounts receivable under program	$ 289,000	$ 609,000	$ 385,000
Percentage of credit exchange receivable	65.00%