Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Significant Accounting Policies [Line Items]
Trade accounts payable	$ 495,000	$ 155,000
Depreciation expense	7,448,000	6,272,000	6,769,000
Goodwill, carrying amount	9,730,000	9,730,000	9,730,000
Money market mutual fund	3,700,000
Cash and cash equivalents, deposited at major financial institutions	4,300,000
Number of major financial institutions	3
Uninsured Cash and Cash Equivalents	6,200,000
Allowances for doubtful account balances	$ 47,000	$ 42,000
Maximum
Significant Accounting Policies [Line Items]
Cash equivalents, original maturities	90 days
Credit Concentration Risk | Accounts Receivable
Significant Accounting Policies [Line Items]
Largest customer, percentage of accounts receivable	16.30%	6.70%	16.20%
Patents and licenses | Maximum
Significant Accounting Policies [Line Items]
Patents and licenses, useful lives	19 years
Patents and licenses | Minimum
Significant Accounting Policies [Line Items]
Patents and licenses, useful lives	7 years