Stockholders' Equity (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Jun. 30, 2019	Dec. 31, 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
Common Stock, Shares, Issued			37,598,747	37,161,068
Common Stock, Shares, Outstanding			31,899,997	31,647,284
At-The-Market Equity Offering Program [Member]
Stock Issuance Program, Maximum Amount Authorized		$ 12,000,000
Shares Issued, Price Per Share	$ 9.32	$ 9.76
At-The-Market Equity Offering Program [Member] | Common Stock [Member]
Stock Issued During Period, Value, New Issues	$ 23,000	$ 1,200,000
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