Summarized Quarterly Financial Data (unaudited) (Tables)

12 Months Ended

Dec. 31, 2018

Quarterly Financial Information Disclosure [Abstract]

Summarized quarterly financial data

	2018								2017
		Q1		Q2		Q3		Q4		Q1		Q2		Q3		Q4
Revenue	$	8,177,000	$	7,488,000	$	7,884,000	$	6,487,000	$	2,379,000	$	2,689,000	$	3,089,000	$	4,953,000
Net income (loss)	$	1,693,000	$	1,799,000	$	3,119,000	$	5,351,000	$	58,000	$	365,000	$	1,001,000	$	733,000
Net income (loss) per share:
Continuing operations	$	0.06	$	0.07	$	0.11	$	0.20	$	0.00	$	0.02	$	0.05	$	0.03
Discontinued operations		—		—		—		—		—		—		—		—