Public Offering (Details) - USD ($) $ / shares in Units, $ in Millions			12 Months Ended
	Jun. 08, 2017	May 15, 2017	Dec. 31, 2019	Dec. 31, 2017	Aug. 19, 2019	May 09, 2017
Class of Stock [Line Items]
Public offering price (dollars per share)					$ 17.99
Common Stock
Class of Stock [Line Items]
Issuance of common stock and warrants (shares)			56,000	3,085,000
Shares to the Public
Class of Stock [Line Items]
Sale of stock (shares)	3,085,484	2,750,000
Public Offering
Class of Stock [Line Items]
Public offering price (dollars per share)		$ 28.85
Underwriting discounts and commissions (dollars per share)						$ 1.73
Gross proceeds from sale of common stock	$ 89.0
Underwriting discounts, commissions and other costs	5.8
Net proceeds	$ 83.2
Underwriters
Class of Stock [Line Items]
Sale of stock (shares)	335,484
Underwriters | Common Stock
Class of Stock [Line Items]
Issuance of common stock and warrants (shares)		412,500