Stockholders' Equity (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2018	Jun. 30, 2018
Capital Stock Shares Authorised				120,000,000
Common Stock, Shares Authorized	79,999,997		79,999,997
Common Stock, Par or Stated Value Per Share	$ 0.01		$ 0.01
Preferred Stock, Shares Authorized	2		2
Preferred Stock, Par or Stated Value Per Share	$ 0.01		$ 0.01
Special Stock, Par or Stated Value Per Share	$ 0.01		$ 0.01
Special Stock, Shares Authorized	1		1
Common Stock, Shares, Issued	36,803,218		37,156,068
Common Stock, Shares, Outstanding	31,451,796		31,644,345
At-The-Market Equity Offering Program [Member]
Stock Issued During Period, Value, New Issues	$ 23,000	$ 1,200,000
Stock Issuance Program, Maximum Amount Authorized		$ 12,000,000
Shares Issued, Price Per Share	$ 9.32	$ 9.76
Stock Issuance Program, Remaining Amount Authorized			$ 10,800,000
At-The-Market Equity Offering Program [Member] | Common Stock [Member]
Stock Issued During Period, Shares, New Issues	2,492	120,299
Blank Check Preferred Stock [Member]
Preferred Stock, Shares Authorized	40,000,000		40,000,000
Preferred Stock, Par or Stated Value Per Share	$ 0.01		$ 0.01
Blank Check Preferred Stock [Member] | Preferred Stock [Member]
Preferred Stock, Shares Authorized			40,000,000