Stockholders' Equity (Details) - USD ($)		6 Months Ended
	Aug. 06, 2018	Jun. 30, 2018	Dec. 31, 2017	Aug. 29, 2011
Equity Class Of Treasury Stock [Line Items]
Number of shares authorized and available for repurchase (in shares)		540,000		100,000
Treasury stock, shares (in shares)		81,584	81,584
Value of repurchased common stock		$ 580,000	$ 580,000
Dividend declaration date		Aug. 06, 2013
Dividend date of record		Jul. 29, 2013
Number of warrants received for each share of common stock (in shares)		5
Number of warrants that entitle holder to purchase one share of common stock (in shares)		25
Number of common shares callable by warrants (in shares)		1
Warrant exercise price (in dollars per share)		$ 7.50
Subsequent Event [Member]
Equity Class Of Treasury Stock [Line Items]
Gross proceeds from warrant exercises	$ 926,948
Issuance of shares on exercise of warrants	123,593