Correction of an Immaterial Prior Year Error (Details) - USD ($)		3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Net income available to common stockholders	$ 855,000	$ 1,815,000	$ 855,000	$ 855,000
Prior Year Adjustment [Member]
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Net income available to common stockholders	787,000
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	$ 68,000				$ 511,000