Taxes - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Tax Credit Carryforward [Line Items]
Effective tax rate excluding effect of discrete event	19.00%
Increase in liability, net of deferred tax benefit, for uncertain tax positions	$ 644,000
Increase (decrease) in interest and penalties	38,000
Reserve for income taxes, total	5,955,000
Reserve for income taxes, noncurrent	5,955,000	5,216,000
Interest and penalties, gross	1,247,000
Reserve for income taxes to be recorded in additional paid in capital	405,000
Minimum decrease in income tax expense due to release in reserves	1,600,000
Maximum decrease in income tax expense due to release in reserves	1,800,000
Tax years open to examination by various taxing authorities	2008 through 2012
Tax years open to examination by various taxing authorities for other entities	2006 through 2012
Research and development tax credit [Member]
Tax Credit Carryforward [Line Items]
Reduction in tax expense	555,000
Research and development tax expense [Member]
Tax Credit Carryforward [Line Items]
Reduction in tax expense	$ 370,000