Income Taxes - Additional Information (Detail) (USD $)	1 Months Ended	12 Months Ended
	Aug. 31, 2004	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Taxes [Line Items]
Deferred tax assets		$ 784,600,000	$ 718,200,000
Deferred tax liabilities		34,400,000	28,800,000
Change in the valuation allowance		60,700,000	57,200,000	56,500,000
Federal operating loss carryforwards		1,600,000,000
State operating loss carryforwards		1,100,000,000
Net operating loss carryforwards	216,000,000
Net operating loss and credit carryforwards, annual use limitation	13,000,000
Research and development credits subject to expiration		$ 77,400,000
Research and development credits, expiration year		2033
Minimum
Income Taxes [Line Items]
Net operating loss carry-forwards, expiration year		2013
Maximum
Income Taxes [Line Items]
Net operating loss carry-forwards, expiration year		2014