Fair Value Measurements - Additional Information (Detail) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Transfer of assets and liabilities between levels		$ 0
Loss recorded in research and development due to change in fair value of contingent consideration liabilities	$ 0	0	$ 42,000
Money Market Funds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash Equivalents, at Carrying Value		168,123,000		$ 3,057,000
Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash Equivalents, at Carrying Value		$ 168,123,000		$ 3,057,000