Net Income (Loss) Per Common Share (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands				12 Months Ended
	Jun. 05, 2018	Jun. 01, 2018	May 25, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Proceeds from issuance of common stock net of underwriting discount and other offering fees and expenses				$ 32,246
Stock Compensation Plan [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount				323,250	590,350	844,000
Weighted average price of anti-dilutive options outstanding				$ 32.36	$ 30.63	$ 27.13
Convertible Notes [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount					268,351	408,459
Options And Restricted Stock Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount						6,575
Underwritten Public Offering [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Gross proceeds from issuance of common stock		$ 34,500
Proceeds from issuance of common stock net of underwriting discount and other offering fees and expenses		$ 32,200
Public offering’s impact on weighted average number of shares				800,000
Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares issued during period				1,408,163
Common Stock [Member] | Underwritten Public Offering [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares issued during period	183,673		1,224,490
Shares issued price per share			$ 24.50
Underwriters purchase option period			30 days