Accounting For Stock-Based Compensation (Narrative) (Details)			3 Months Ended		9 Months Ended
	May 10, 2018 USD ($) $ / shares shares	May 11, 2017 USD ($) $ / shares shares	Sep. 30, 2018 USD ($) qtr stock-based_complensation_plan shares	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) qtr stock-based_complensation_plan $ / shares shares	Sep. 30, 2017 USD ($)	Dec. 31, 2017 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			504,875		504,875		568,525
Weighted average grant date fair value (in dollars per share) | $ / shares					$ 16.25
Excess tax benefit from the exercise of stock options			$ 37,000		$ 70,000	$ 207,000
Aggregate fair value of outstanding restricted shares and restricted stock units			1,000,000.0		1,000,000.0
Aggregate fair value of restricted shares and restricted stock units					177,000
Proceeds from exercise of stock options					452,000	330,000
Fair value of shares vested					$ 204,000
Shares, Granted (in shares) | shares					8,000
Equity based compensation expense			217,000	$ 240,000	$ 701,000	640,000
Unrecognized compensation cost related to non-vested equity based compensation			$ 1,500,000		$ 1,500,000
Unrecognized equity based compensation weighted average period, years					2 years 4 months 9 days
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance pursuant to outstanding awards | shares			534,087		534,087
Vesting period, years					4 years
Expiration of stock options from date of grant					7 years
Number of shares available for future issuance (in shares) | shares			336,489		336,489
Weighted average remaining contractual term, years					3 years 9 months 18 days
Aggregate intrinsic value for all options outstanding			$ 5,200,000		$ 5,200,000
Weighted average remaining contractual term for exercisable options, years					3 years
Aggregate intrinsic value of exercisable options			3,700,000		$ 3,700,000
Aggregate intrinsic value of stock options exercised					572,000
Proceeds from exercise of stock options					452,000	330,000
Equity based compensation expense			94,000	116,000	$ 328,000	345,000
Restricted Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant date fair value (in dollars per share) | $ / shares					$ 16.25
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			$ 59,000	49,000	$ 176,000	145,000
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
Number of additional shares authorized for issuance | shares					150,000
Shares, Granted (in shares) | shares					16,403
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	33,000	$ 86,000	85,000
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]
Common stock reserved for issuance pursuant to outstanding awards | shares			16,000		16,000
Number of shares available for future issuance (in shares) | shares			60,000		60,000
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	8,000
Stock granted, value	$ 130,000	$ 167,000
Weighted average grant date fair value (in dollars per share) | $ / shares	$ 16.25	$ 20.90
Aggregate intrinsic value for all options outstanding			$ 121,000		$ 121,000
Number of shares vested | shares					2,000
Equity based compensation expense			$ 33,000	$ 42,000	$ 111,000	$ 65,000
Non Employee Director Stock Plan [Member] | Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, Granted (in shares) | shares		2,000