Stock-Based Compensation And Stock Repurchases (Narrative) (Details) - USD ($)		3 Months Ended		6 Months Ended		12 Months Ended
	Nov. 07, 2017	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017	Sep. 30, 2017	Mar. 02, 2017	Dec. 31, 2016
Equity And Stock-Based Compensation [Line Items]
Shares granted		0
Stock Option [Member]
Equity And Stock-Based Compensation [Line Items]
Grant date fair value of options vesting		$ 112,000	$ 84,000	$ 197,000	$ 139,000
Unrecognized estimated compensation cost related to non-vested stock options granted		1,100,000		$ 1,100,000
Recognition period of unrecognized compensation cost				1 year 9 months 7 days
Intrinsic unrealized value of all options outstanding, vested and expected to vest		2,200,000		$ 2,200,000
Percentage of option currently exercisable				82.60%
Restricted Stock Units (RSUs) [Member]
Equity And Stock-Based Compensation [Line Items]
Compensation expense		227,000	$ 180,000	$ 521,000	$ 299,000
Unrecognized estimated compensation cost related to non-vested stock options granted		1,500,000		$ 1,500,000
Vesting period of stock options and RSU				1 year 1 month 6 days
Restricted Stock Units (RSUs) [Member] | Directors [Member]
Equity And Stock-Based Compensation [Line Items]
Percentage of shares vested				100.00%
Restricted Stock Units (RSUs) [Member] | Management [Member]
Equity And Stock-Based Compensation [Line Items]
Vesting period of stock options and RSU				4 years
Percentage of shares vested				25.00%
2014 Stock Repurchase Plan [Member]
Equity And Stock-Based Compensation [Line Items]
Repurchase program, amount authorized									$ 10,000,000
$25 Million Stock Repurchase Program [Member]
Equity And Stock-Based Compensation [Line Items]
Repurchase program, remaining amount authorized		$ 18,100,000		$ 18,100,000
Shares repurchased		5,000
Class A Nonvoting Common Stock [Member]
Equity And Stock-Based Compensation [Line Items]
Common Stock authorized for issuance under 2010 Stock Incentive Plan		2,197,460		2,197,460
Class A [Member]
Equity And Stock-Based Compensation [Line Items]
Shares granted				126,840		169,762
Stock options terminated						2,500
Class A [Member] | $25 Million Stock Repurchase Program [Member]
Equity And Stock-Based Compensation [Line Items]
Repurchase value		$ 6,900,000		$ 6,900,000
Repurchase program, amount authorized								$ 25,000,000
Share price				$ 15.97
Shares repurchased				433,361
Class A [Member] | $25 Million Stock Repurchased At $16.80 [Member]
Equity And Stock-Based Compensation [Line Items]
Payment to repurchase shares				$ 397,000
Share price				$ 16.80
Shares repurchased				23,638
Minimum [Member]
Equity And Stock-Based Compensation [Line Items]
Vesting period of stock options and RSU				0 years
Maximum [Member]
Equity And Stock-Based Compensation [Line Items]
Vesting period of stock options and RSU				4 years
2010 Stock Incentive Plan [Member]
Equity And Stock-Based Compensation [Line Items]
Additional shares authorized	947,460
2010 Stock Incentive Plan [Member] | Class A Nonvoting Common Stock [Member]
Equity And Stock-Based Compensation [Line Items]
Common Stock authorized for issuance under 2010 Stock Incentive Plan							1,250,000
Common Stock shares remaining for future issuances		1,176,342		1,176,342
Repurchase program, shares available							302,540