Stock-Based Compensation (Narrative) (Details)		3 Months Ended		6 Months Ended
	May 16, 2019 USD ($) $ / shares shares	Jun. 30, 2019 USD ($) qtr stock-based_complensation_plan shares	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) qtr stock-based_complensation_plan $ / shares shares	Jun. 30, 2018 USD ($)	Dec. 31, 2018 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 | shares		504,092		504,092		523,042
Weighted average grant date fair value (in dollars per share) | $ / shares				$ 17.26
Number of shares vested | shares				4,000
Aggregate fair value of outstanding restricted shares and restricted stock units		$ 966,000		$ 966,000
Aggregate fair value of restricted shares and restricted stock units				77,000
Proceeds from exercise of stock options				$ 59,000	$ 251,000
Shares, Granted (in shares) | shares				8,000
Equity based compensation expense		249,000	$ 225,000	$ 493,000	484,000
Unrecognized compensation cost related to non-vested equity based compensation		$ 1,800,000		$ 1,800,000
Unrecognized equity based compensation weighted average period, years				2 years 7 months 2 days
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for future issuance (in shares) | shares		273,764		273,764
Common stock reserved for issuance pursuant to outstanding awards | shares		539,628		539,628
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		$ 2,900,000		$ 2,900,000
Weighted average remaining contractual term for exercisable options, years				2 years 9 months 18 days
Aggregate intrinsic value of exercisable options		2,600,000		$ 2,600,000
Aggregate intrinsic value of stock options exercised				57,000
Proceeds from exercise of stock options				59,000	251,000
Fair value of shares vested				5,000
Equity based compensation expense		110,000	109,000	$ 217,000	234,000
Restricted Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, Granted (in shares) | 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 | shares				1
Shares, Granted (in shares) | shares				0
Equity based compensation expense		$ 77,000	58,000	$ 153,000	117,000
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		174,469		174,469
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		$ 31,000	21,000	$ 60,000	55,000
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) | shares		52,000		52,000
Common stock reserved for issuance pursuant to outstanding awards | shares		16,000		16,000
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		4
Stock issued during period, shares | shares	8,000
Stock granted, value	$ 138,000
Weighted average grant date fair value (in dollars per share) | $ / shares	$ 17.26
Aggregate intrinsic value for all options outstanding		$ 130,000		$ 130,000
Number of shares vested | shares				0
Equity based compensation expense		$ 31,000	$ 37,000	$ 63,000	$ 78,000