Share-Based Compensation (Narrative) (Details)		3 Months Ended		6 Months Ended
	May 13, 2021 USD ($) $ / shares shares	Jun. 30, 2021 USD ($) qtr stock-based_complensation_plan shares	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($) qtr stock-based_complensation_plan $ / shares shares	Jun. 30, 2020 USD ($) shares	Dec. 31, 2020 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		411,225		411,225		419,100
Weighted average grant date fair value (in dollars per share) | $ / shares				$ 27.96
Number of shares vested				4,000
Aggregate fair value of outstanding restricted shares and restricted stock units | $		$ 3,000,000.0		$ 3,000,000.0
Aggregate fair value of restricted shares and restricted stock units | $				115,000	$ 102,000
Proceeds from exercise of stock options | $				$ 67,000	$ 256,000
Number of shares vested				0	0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants, Forfeitures and Expirations in Period				0
Shares, Granted (in shares)				8,000
Unvested shares		72,454		72,454		68,454
Equity based compensation expense | $		$ 337,000	$ 286,000	$ 671,000	$ 558,000
Unrecognized compensation cost related to non-vested equity based compensation | $		$ 2,300,000		$ 2,300,000
Unrecognized equity based compensation weighted average period, years				2 years 6 months 3 days
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for future issuance (in shares)		124,501		124,501
Common stock reserved for issuance pursuant to outstanding awards		467,679		467,679
Vesting period, years				4 years
Expiration of stock options from date of grant				7 years
Weighted average remaining contractual term, years				3 years 1 month 13 days
Aggregate intrinsic value for all options outstanding | $		$ 10,600,000		$ 10,600,000
Weighted average remaining contractual term for exercisable options, years				2 years 2 months 4 days
Aggregate intrinsic value of exercisable options | $		8,000,000.0		$ 8,000,000.0
Aggregate intrinsic value of stock options exercised | $				87,000	2,100,000
Proceeds from exercise of stock options | $				67,000	256,000
Equity based compensation expense | $		125,000	114,000	$ 248,000	228,000
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 | $		$ 124,000	101,000	$ 247,000	202,000
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for future issuance (in shares)		136,971		136,971
Maximum contribution per plan year | $				$ 6,500
Equity based compensation expense | $		$ 31,000	25,000	$ 63,000	48,000
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%
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)		36,000		36,000
Common stock reserved for issuance pursuant to outstanding awards		8,000		8,000
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 | $	$ 224,000
Weighted average grant date fair value (in dollars per share) | $ / shares	$ 27.96
Number of shares vested				0
Unvested shares		8,000		8,000
Aggregate fair value of the unvested shares based on the closing price of entity's common stock | $		$ 328,000		$ 328,000
Equity based compensation expense | $		$ 57,000	$ 46,000	$ 113,000	$ 80,000