Description of Business - Additional Information (Details) - USD ($) $ in Thousands, shares in Millions	1 Months Ended				3 Months Ended
	Mar. 31, 2019	Oct. 31, 2018	Jul. 31, 2018	Jan. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Subsidiary, Sale of Stock [Line Items]
Proceeds from sale of common stock, net					$ 68,273	$ 0
Shares sold in offering	5.2
At The Market Equity Offering
Subsidiary, Sale of Stock [Line Items]
Proceeds from sale of common stock, net				$ 40,000
Public Stock Offering
Subsidiary, Sale of Stock [Line Items]
Shares sold in offering	2.5		4.6
Total gross proceeds from stock offering	$ 73,000		$ 57,500
Aggregate net proceeds from stock offering	$ 68,300		$ 53,800
Selling Stockholder [Member]
Subsidiary, Sale of Stock [Line Items]
Shares sold in offering	2.0
Over-Allotment Option [Member]
Subsidiary, Sale of Stock [Line Items]
Shares sold in offering	0.7		0.6
Term Loan Agreement
Subsidiary, Sale of Stock [Line Items]
Debt Instrument, Redemption Price, Percentage		4.00%
Upfront Fee Of Aggregate Principal Amount, Percentage		0.50%
Minimum | Term Loan Agreement
Subsidiary, Sale of Stock [Line Items]
Debt Instrument, Redemption Price, Percentage		1.00%