Description of Business - Additional Information (Details) - USD ($) $ in Thousands, shares in Millions	1 Months Ended		9 Months Ended
	Jul. 31, 2018	Jan. 31, 2018	Sep. 30, 2018	Sep. 30, 2017
Subsidiary, Sale of Stock [Line Items]
Proceeds from sale of common stock, net			$ 53,847	$ 56,486
At The Market Equity Offering
Subsidiary, Sale of Stock [Line Items]
Proceeds from sale of common stock, net		$ 40,000
Commission expense, percentage		3.00%
Public Stock Offering
Subsidiary, Sale of Stock [Line Items]
Shares sold in offering	4.6
Total gross proceeds from stock offering	$ 57,500
Aggregate net proceeds from stock offering	$ 53,800
Over-Allotment Option [Member]
Subsidiary, Sale of Stock [Line Items]
Shares sold in offering	0.6