Stock-Based Compensation - Additional Information (Detail) (USD $)	0 Months Ended	1 Months Ended	3 Months Ended		9 Months Ended		3 Months Ended	9 Months Ended	1 Months Ended	0 Months Ended	9 Months Ended
	Apr. 30, 2014	Jan. 31, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 Performance-Based [Member]	Sep. 30, 2014 Performance-Based [Member]	Jun. 30, 2014 Investigational New Drug [Member]	Aug. 29, 2014 Employee Stock Purchase Plan [Member]	Sep. 30, 2014 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation granted under plan vest period					4 years
Term of award					10 years
Stock-based compensation expense			$ 4,649,000	$ 3,487,000	$ 14,578,000	$ 7,476,000	$ 100,000	$ 700,000
Percentage of performance award									20.00%
Percentage of closing price of common stock											85.00%
Common stock purchase										24,516	46,290
Proceeds from issuance of common stock	$ 94,500,000	$ 2,100,000				$ 123,000,000				$ 500,000	$ 1,000,000