Business and Basis of Presentation - Restatement Corrections and Other Immaterial Adjustments on Condensed Consolidated Results of Operations (Detail) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
As Reported [Member]
Research and development	$ 10,501,000	$ 9,583,000	$ 22,482,000	$ 18,474,000
Selling, general and administrative	22,629,000	23,347,000	44,976,000	41,609,000
Amortization and impairment of purchased intangible assets	3,372,000	1,636,000	5,740,000	2,566,000
Total operating costs and expenses	43,770,000	46,140,000	87,248,000	82,896,000
(Loss) income from operations	(10,538,000)	22,562,000	(15,349,000)	45,665,000
Income (loss) before income taxes	(10,701,000)	21,055,000	(16,830,000)	44,296,000
(Provision) benefit for income taxes	524,000	(2,985,000)	3,864,000	20,316,000
Net income (loss)	(10,177,000)	18,070,000	(12,966,000)	64,612,000
Net income (loss) per share, basic	$ (0.17)	$ 0.31	$ (0.22)	$ 1.10
Net income (loss) per share, diluted	$ (0.17)	$ 0.29	$ (0.22)	$ 1.01
As Restated [Member]
Research and development	104,660,000	9,288,000	22,343,000	17,819,000
Selling, general and administrative	22,584,000	23,176,000	44,598,000	41,305,000
Amortization and impairment of purchased intangible assets	5,449,000	1,636,000	9,894,000	2,566,000
Total operating costs and expenses	45,761,000	45,674,000	90,885,000	81,937,000
(Loss) income from operations	(12,529,000)	23,028,000	(18,986,000)	46,624,000
Income (loss) before income taxes	(12,692,000)	21,521,000	(20,467,000)	45,255,000
(Provision) benefit for income taxes	2,971,000	(3,171,000)	5,310,000	19,932,000
Net income (loss)	$ (9,721,000)	$ 18,350,000	$ (15,157,000)	$ 65,187,000
Net income (loss) per share, basic	$ (0.16)	$ 0.31	$ (0.26)	$ 1.11
Net income (loss) per share, diluted	$ (0.16)	$ 0.29	$ (0.26)	$ 1.02