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Net Income (Loss) Per Common Share (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands					3 Months Ended		9 Months Ended
	Jun. 05, 2018	Jun. 05, 2018	Jun. 01, 2018	May 25, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 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							$ 32,246
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					236,000	495,675	261,000	566,075
Weighted average price of anti-dilutive options outstanding					$ 34.53	$ 31.74	$ 33.86	$ 30.21
Exercise of Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount						121,750		99,638
Issuance of Stock for 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						39,216		29,101
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					1,400,000		700,000
Common Stock [Member] \| Underwritten Public Offering [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares issued during period	183,673	1,408,163		1,224,490
Shares issued price per share				$ 24.50
Underwriters purchase option period				30 days