International Business Machines Corporation Alliance - Additional Information (Detail) (USD $)	1 Months Ended		12 Months Ended
	May 17, 2008	Dec. 16, 2007	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008	Dec. 31, 2007
Alliance Agreement [Line Items]
Description of alliance agreement amendment	On March 17, 2008, the Company and IBM entered into Amendment No. 1 to the Alliance (“Amendment No. 1” and included hereafter in all references to the “Alliance”), which changed the timing of certain payments to be made by IBM.
Common stock warrants, exercise date	5 years
Common stock warrants			$ 24,003,000	$ 24,003,000
Consideration received for the estimated fair value of common stock warrants		33,300,000				37,300,000
Alliance agreement liability			20,667,000	22,584,000	32,487,000		9,300,000
Refundable subject to achievement of future milestones			20,700,000	20,700,000
Alliance agreement liability, current			20,667,000	1,917,000
Alliance agreement liability, noncurrent				20,667,000
Costs related to fulfillment of technical enablement milestones			$ 1,917,000	$ 9,903,000	$ 11,000,000
Stated initial term of the Alliance			5 years
Warrant 1
Alliance Agreement [Line Items]
Common stock warrants, exercise price	27.50
Warrant 1 | Maximum
Alliance Agreement [Line Items]
Issuance of warrants to IBM to purchase common stock	1,427,035
Warrant 2
Alliance Agreement [Line Items]
Common stock warrants, exercise price	33.00
Warrant 2 | Maximum
Alliance Agreement [Line Items]
Issuance of warrants to IBM to purchase common stock	1,427,035