Share-Based Compensation (Narrative) (Details)		3 Months Ended
	May 14, 2020 USD ($) $ / shares shares	Mar. 31, 2021 USD ($) qtr stock-based_complensation_plan shares	Mar. 31, 2020 USD ($) 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
Common stock reserved for issuance pursuant to outstanding awards | shares		411,850		419,100
Number of shares vested | shares		2,000
Aggregate fair value of outstanding restricted shares and restricted stock units		$ 1,700,000
Aggregate fair value of restricted shares and restricted stock units		56,000	$ 45,000
Proceeds from exercise of stock options		$ 57,000	$ 85,000
Number of shares vested | shares		0	0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants, Forfeitures and Expirations in Period | shares		0
Unvested shares | shares		66,454		68,454
Equity based compensation expense		$ 334,000	$ 272,000
Unrecognized compensation cost related to non-vested equity based compensation		$ 2,400,000
Unrecognized equity based compensation weighted average period, years		2 years 9 months 10 days
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for future issuance (in shares) | shares		124,501
Common stock reserved for issuance pursuant to outstanding awards | shares		468,304
Vesting period, years		4 years
Expiration of stock options from date of grant		7 years
Weighted average remaining contractual term, years		3 years 4 months 13 days
Aggregate intrinsic value for all options outstanding		$ 4,500,000
Weighted average remaining contractual term for exercisable options, years		2 years 5 months 8 days
Aggregate intrinsic value of exercisable options		$ 3,800,000
Aggregate intrinsic value of stock options exercised		78,000	140,000
Proceeds from exercise of stock options		57,000	85,000
Equity based compensation expense		$ 123,000	114,000
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 | shares		1
Equity based compensation expense		$ 123,000	101,000
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for future issuance (in shares) | shares		136,971
Maximum contribution per plan year		$ 6,500
Equity based compensation expense		$ 32,000	23,000
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) | shares		44,000
Common stock reserved for issuance pursuant to outstanding awards | shares		8,000
Number of shares granted for non-employee directors upon re-election, shares | shares		2,000
Number of quarterly installments in which awards will vest | qtr		4
Stock issued during period, shares | shares	8,000
Stock granted, value	$ 227,000
Weighted average grant date fair value (in dollars per share) | $ / shares	$ 28.34
Number of shares vested | shares		6,000
Unvested shares | shares		2,000
Aggregate fair value of the unvested shares based on the closing price of entity's common stock		$ 52,000
Equity based compensation expense		$ 56,000	$ 34,000