Description of Business - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended	6 Months Ended
	Jan. 31, 2018	Jun. 30, 2018	Jun. 30, 2017
Subsidiary, Sale of Stock [Line Items]
Proceeds from sale of common stock, net		$ 0	$ 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%