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Share-based Compensation - Expense Other (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share-based Compensation Expense
Total compensation cost	$ 636,000	$ 849,000	$ 2,532,000	$ 2,902,000
Unrecognized compensation cost	4,600,000		4,600,000
Stock options
Share-based Compensation Expense
Total compensation cost	601,000	719,000	$ 2,400,000	2,600,000
Compensation cost not yet recognized, period for recognition			2 years 7 months 6 days
Shares issued upon the exercise of outstanding stock options			36,040
RSUs outstanding
Share-based Compensation Expense
Total compensation cost	35,000	$ 129,000	$ 130,000	$ 266,000
Compensation cost not yet recognized, period for recognition			2 years 2 months 12 days
Restricted stock
Share-based Compensation Expense
Unrecognized compensation cost	$ 0		$ 0