Equity - Options (Details) - USD ($)	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Stock Based Compensation Plans
Options exercised (in shares)	5,000	3,334
Weighted Average Exercise Price (in dollars per share)	$ 24.65	$ 23.79
Value of options exercised	$ 123,000	$ 79,000
Market value of options on the date of exercise	$ 205,000	$ 154,000
Options outstanding at end of the period (in shares)	20,000
Options exercisable at end of the period (in shares)	20,000
2015 Plan
Stock Based Compensation Plans
Total shares reserved for issuance of common stock related to the conversion of preferred stock	1,400,000
Stock options granted (in shares)	0	0
Stock options
Stock Based Compensation Plans
Compensation expense related to share-based award	$ 0	$ 2,000