Shareholders' Equity (Statement of Equity) (Details) - USD ($)	3 Months Ended						9 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Sep. 30, 2017	Sep. 30, 2016
Class of Stock [Line Items]
Net Income	$ 2,862,000			$ 3,165,000			$ 12,277,000	$ 11,953,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance			$ 234,242,000				234,242,000
Other comprehensive income (loss), net of tax							$ 50,000
Exercise of stock options (in shares)							74,699
Exercise of stock options							$ 1,423,000
Issuance of restricted common stock for services (in shares)	3,170	3,195	3,985	3,485	3,925	5,190
Issuance of restricted common stock for services	$ 97,000	$ 97,000	$ 97,000	$ 97,000	$ 97,000	$ 97,000	$ 290,000
Issuance of common stock under Employee Stock Purchase Plan (in shares)							30,650	37,749
Issuance of common stock under Employee Stock Purchase Plan							$ 698,000
Compensation cost of stock options							1,322,000
Balance	$ 250,302,000						$ 250,302,000
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance (in shares)			14,413,000				14,413,000
Balance			$ 144,000				$ 144,000
Exercise of stock options (in shares)							75,000
Exercise of stock options							$ 1,000
Issuance of restricted common stock for services (in shares)							10,000
Issuance of restricted common stock for services							$ 0
Issuance of common stock under Employee Stock Purchase Plan (in shares)							31,000
Issuance of common stock under Employee Stock Purchase Plan							$ 0
Balance (in shares)	14,529,000						14,529,000
Balance	$ 145,000						$ 145,000
Additional Paid-In Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance			87,319,000				87,319,000
Exercise of stock options							1,422,000
Issuance of restricted common stock for services							290,000
Issuance of common stock under Employee Stock Purchase Plan							698,000
Compensation cost of stock options							1,322,000
Balance	91,051,000						91,051,000
Retained Earnings
Class of Stock [Line Items]
Net Income							12,277,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance			158,432,000				158,432,000
Balance	170,709,000						170,709,000
Treasury Stock, Common [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance			(3,042,000)				(3,042,000)
Balance	(3,042,000)						(3,042,000)
Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance			$ (8,611,000)				(8,611,000)
Other comprehensive income (loss), net of tax							50,000
Balance	$ (8,561,000)						$ (8,561,000)