Stockholders' Equity - Additional Information (Details) - USD ($)	1 Months Ended	3 Months Ended	9 Months Ended
	May 31, 2016	Sep. 30, 2016	Sep. 30, 2016	Sep. 30, 2015
Stockholders’ Equity [Line Items]
Net proceeds from issuance of common stock, after deducting commissions and expenses payable			$ 31,849,000	$ 150,283,000
At-the-Market Offering | Sales Agreement | Cowen and Company, LLC
Stockholders’ Equity [Line Items]
Commission on sales of common stock, percentage	3.00%
Issuance of common stock (in shares)		2,180,477	2,180,477
Net proceeds from issuance of common stock, after deducting commissions and expenses payable		$ 31,800,000	$ 31,800,000
Aggregate offering available for issuance of common stock			$ 67,200,000
At-the-Market Offering | Sales Agreement | Cowen and Company, LLC | Maximum
Stockholders’ Equity [Line Items]
Aggregate offering from offer and sell of common stock	$ 100,000,000