Share-Based Compensation (Narrative) (Details)		3 Months Ended		6 Months Ended
	May 14, 2020 USD ($) $ / shares shares	Jun. 30, 2020 USD ($) qtr stock-based_complensation_plan shares	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) qtr stock-based_complensation_plan $ / shares shares	Jun. 30, 2019 USD ($) shares	Dec. 31, 2019 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of stock-based compensation plans | stock-based_complensation_plan		3		3
Common stock reserved for issuance pursuant to outstanding awards		415,900		415,900		520,513
Weighted average grant date fair value (in dollars per share) | $ / shares				$ 28.34
Number of shares vested				4,000
Aggregate fair value of outstanding restricted shares and restricted stock units | $		$ 2,300,000		$ 2,300,000
Aggregate fair value of restricted shares and restricted stock units | $				102,000	$ 77,000
Proceeds from exercise of stock options | $				$ 256,000	59,000
Number of shares vested				0
Shares, Granted (in shares)				8,000
Unvested shares		72,204		72,204		68,204
Equity based compensation expense | $		$ 286,000	$ 249,000	$ 558,000	493,000
Unrecognized compensation cost related to non-vested equity based compensation | $		$ 2,000,000.0		$ 2,000,000.0
Unrecognized equity based compensation weighted average period, years				2 years 6 months
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for future issuance (in shares)		185,351		185,351
Common stock reserved for issuance pursuant to outstanding awards		468,104		468,104
Vesting period, years				4 years
Expiration of stock options from date of grant				7 years
Weighted average remaining contractual term, years				3 years 6 months
Aggregate intrinsic value for all options outstanding | $		$ 7,800,000		$ 7,800,000
Weighted average remaining contractual term for exercisable options, years				2 years 6 months
Aggregate intrinsic value of exercisable options | $		5,700,000		$ 5,700,000
Aggregate intrinsic value of stock options exercised | $				2,100,000	57,000
Proceeds from exercise of stock options | $				256,000	59,000
Equity based compensation expense | $		114,000	110,000	$ 228,000	217,000
Restricted Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, Granted (in shares)				8,000
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period, years				4 years
Restricted stock units to common stock ratio, shares entitled, shares				1
Shares, Granted (in shares)				0
Equity based compensation expense | $		$ 101,000	77,000	$ 202,000	$ 153,000
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for future issuance (in shares)		156,688		156,688
Shares, Granted (in shares)				0	0
Maximum contribution per plan year | $				$ 6,500
Employees can purchase stock at the percentage rate of the lower of the market price on the first or last day of the offering period (as a percent)				85.00%
Equity based compensation expense | $		$ 25,000	31,000	$ 48,000	$ 60,000
Employee Stock Purchase Plan | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Payroll deduction for employee stock purchase plan percentage				1.00%
Employee Stock Purchase Plan | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Payroll deduction for employee stock purchase plan percentage				10.00%
Non Employee Director Stock Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for future issuance (in shares)		44,000		44,000
Common stock reserved for issuance pursuant to outstanding awards		12,000		12,000
Number of shares granted for non-employee directors upon re-election, shares				2,000
Number of quarterly installments in which awards will vest | qtr		4		4
Stock issued during period, shares	8,000
Stock granted, value | $	$ 226,720
Weighted average grant date fair value (in dollars per share) | $ / shares	$ 28.34
Unvested shares		8,000		8,000
Aggregate fair value of the unvested shares based on the closing price of entity's common stock | $		$ 258,000		$ 258,000
Equity based compensation expense | $		$ 46,000	$ 31,000	$ 80,000	$ 63,000