Fair Value Measurements - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
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
Money Market Funds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash Equivalents, at Carrying Value	130,653,000	$ 133,540,000
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	$ 130,653,000	$ 133,540,000