Stockholders' Equity (Narrative) (Details) $ / shares in Units, $ in Thousands		1 Months Ended	9 Months Ended
	Jun. 11, 2018 USD ($) $ / shares shares	Oct. 31, 2017 USD ($) $ / shares shares	Sep. 30, 2018 $ / shares shares	Dec. 31, 2017 vote $ / shares shares	Sep. 30, 2017 shares
Class of Stock [Line Items]
Shares authorized (in shares)			200,000,000	200,000,000
Vote per share | vote				1
Dividends declared (usd per share) | $ / shares			$ 0
Common stock warrants outstanding (in shares)				1,866,831
Common stock warrant exercise price (in dollars per share) | $ / shares				$ 8.16
Public Offering
Class of Stock [Line Items]
Number of shares issued (in shares)	5,750,000
Price per share (usd per share) | $ / shares	$ 22.25
Consideration received on transaction | $	$ 59,917
Discounts | $	3,678
Offering expenses | $	$ 373
IPO
Class of Stock [Line Items]
Price per share (usd per share) | $ / shares		$ 16.00
Proceeds from IPO | $		$ 125,471
Fees and commissions | $		9,660
Stock issuance costs | $		$ 2,869
IPO | Common Stock
Class of Stock [Line Items]
Number of shares issued (in shares)		8,625,000
Shares authorized (in shares)		200,000,000			10,624,486
The Company | Public Offering
Class of Stock [Line Items]
Number of shares issued (in shares)	2,875,000
Certain Stockholders | Public Offering
Class of Stock [Line Items]
Number of shares issued (in shares)	2,875,000