International Business Machines Corporation Alliance - Additional Information (Detail) (USD $)	1 Months Ended			9 Months Ended	12 Months Ended					1 Months Ended		12 Months Ended			12 Months Ended			1 Months Ended
	Sep. 21, 2012	Mar. 17, 2008	Dec. 16, 2007	Sep. 30, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2008	Dec. 31, 2007	Sep. 21, 2012 Revolving Credit Facility	Feb. 10, 2012 Revolving Credit Facility	Dec. 31, 2012 Warrant One	Mar. 17, 2008 Warrant One	Mar. 17, 2008 Warrant One Maximum	Dec. 31, 2012 Warrant Two	Mar. 17, 2008 Warrant Two	Mar. 17, 2008 Warrant Two Maximum	Sep. 21, 2012 Stock Repurchase Plan 1	Sep. 21, 2012 Stock Repurchase Plan 2
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.
Isssuance of warrants to IBM to purchase common stock														1,427,035			1,427,035
Common stock warrant exercise price												27.50	27.50		33.00	33.00		27.50	33.00
Common stock warrants,exercise date		5 years
Common stock warrants exercised												11,470			350,000
Proceeds from exercises of common stock warrants					$ 11,866,000
Common stock warrants repurchased	2,492,600																	1,415,565	1,077,035
Cash settlement of common stock warrants	5,600,000			29,600,000	29,596,000
Additional amount used to fund share repurchase program	24,000,000									24,000,000	95,000,000
Common stock warrants						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		9,300,000
Alliance agreement liability, current						20,667,000
Costs related to fulfillment of technical enablement milestones						1,917,000	9,900,000
Payment of refundable portion of IBM payments					$ 20,667,000