Stockholders' Equity (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands				3 Months Ended		9 Months Ended
	Jul. 03, 2018	Aug. 09, 2017	Nov. 07, 2016	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Class of Stock [Line Items]
Common stock shares authorized				100,000,000		100,000,000		100,000,000
Common stock, par value				$ 0.01		$ 0.01		$ 0.01
Preferred stock shares authorized				50,000,000		50,000,000		50,000,000
Preferred stock, par value				$ 0.01		$ 0.01		$ 0.01
Common stock shares issued				30,758,852		30,758,852		29,502,624
Common stock shares outstanding				30,758,852		30,758,852		29,502,624
Common stock shares issued related to vesting of restricted stock awards				39,600		300,000
Net proceeds from issuances of common stock						$ 31,230	$ 35,010
2017 Incentive Plan [Member]
Class of Stock [Line Items]
Common stock shares for stock award, available for issuance				1,000,000		1,000,000
First Distribution Agreement [Member]
Class of Stock [Line Items]
Aggregate offering price			$ 50,000
Second Distribution Agreement [Member]
Class of Stock [Line Items]
Aggregate offering price		$ 100,000
Net proceeds from issuances of common stock				$ 17,100
Third Distribution Agreement [Member]
Class of Stock [Line Items]
Aggregate offering price	$ 100,000
Second And Third Distribution Agreements [Member]
Class of Stock [Line Items]
Common stock shares sold and issued				600,000		1,100,000
Net proceeds from issuances of common stock				$ 17,100		$ 31,700
Comissions and fees paid to Sales Agents				$ 300		$ 600
First And Second Distribution Agreements [Member]
Class of Stock [Line Items]
Common stock shares sold and issued					400,000		1,400,000
Net proceeds from issuances of common stock					$ 10,000		$ 34,600
Comissions and fees paid to Sales Agents					$ 200		$ 700