Correction of an Immaterial Prior Year Error (Details) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2016
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Net income available to common stockholders	$ 1,918,000	$ 912,000	$ 3,733,000	$ 1,767,000
Prior Year Adjustment [Member]
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Net income available to common stockholders		845,000		1,600,000
Prior Year Adjustment [Member] | Series B Preferred Stock [Member]
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Discount on redemption of series B preferred stock		$ 67,000		$ 135,000	$ 511,000