Stock-Based Compensation - Additional Information (Detail) (USD $)	0 Months Ended	1 Months Ended	3 Months Ended		6 Months Ended				0 Months Ended	6 Months Ended
	Apr. 29, 2014	Jan. 31, 2013	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 Performance-Based [Member]	Jun. 30, 2014 Investigational New Drug [Member]	Feb. 28, 2014 Employee Stock Purchase Plan [Member]	Jun. 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			$ 5,587,000	$ 2,318,000	$ 9,929,000	$ 3,989,000	$ 600,000
Percentage of performance award								20.00%
Percentage of closing price of common stock										85.00%
Common stock purchase									21,774
Proceeds from issuance of common stock	$ 94,500,000	$ 2,100,000							$ 500,000