Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Taxes [Line Items]
Increase in valuation allowance due to increase in operating losses and tax credit carryforwards	$ 38,300,000	$ 23,000,000	$ 15,200,000
Benefit from (provision for) income taxes	(10,572,000)	0	514,000
Excess tax benefit from exercise of stock options		(120,000)	(220,000)
Net operating loss carryforwards expiration year	2032
Research And Development Tax Credit
Income Taxes [Line Items]
Excess tax benefit from exercise of stock options	500,000
Tax credit carryforwards expiration year	2032
Alternative Minimum Tax
Income Taxes [Line Items]
Tax credit carryforwards	800,000
Net Operating Loss Carryforwards
Income Taxes [Line Items]
Excess tax benefit from exercise of stock options	10,100,000
Federal
Income Taxes [Line Items]
Net operating loss carryforward	272,700,000
Federal | Research And Development Tax Credit
Income Taxes [Line Items]
Tax credit carryforwards	15,300,000
State and Local Jurisdiction
Income Taxes [Line Items]
Net operating loss carryforward	337,800,000
State and Local Jurisdiction | Research And Development Tax Credit
Income Taxes [Line Items]
Tax credit carryforwards	5,600,000
Foreign Tax Authority
Income Taxes [Line Items]
Tax credit carryforwards	$ 3,200,000
Tax credit carryforwards expiration year	2017