Net Income (Loss) Per Common Share (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands					3 Months Ended		6 Months Ended
	Jun. 05, 2018	Jun. 05, 2018	Jun. 01, 2018	May 25, 2018	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
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							$ 32,253
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					265,150	591,700	265,150	616,200
Average price of anti-dilutive options outstanding					$ 34.02	$ 30.26	$ 34.02	$ 29.90
Notes [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount						410,204		408,526
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			$ 32,300
Public offering’s impact on weighted average number of shares					600,000		300,000
Common Stock [Member] | Underwritten Public Offering [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares issued during period	1,408,163	183,673		1,224,490
Shares issued price per share				$ 24.50
Underwriters purchase option period				30 days