Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Income Taxes [Line Items]
Operating loss carryforwards, beginning of expiration year	2013
Operating loss carryforwards, ending of expiration year	2033
Operating loss carryforwards from exercises of stock options	$ 6,100,000
Deferred tax assets, gross	114,127,000	116,809,000
Net change in valuation allowance for deferred tax assets	(2,700,000)	8,100,000
Federal
Income Taxes [Line Items]
Net operating loss carryforwards	226,600,000
State
Income Taxes [Line Items]
Net operating loss carryforwards	$ 195,800,000