Net (loss) Income Per Common Share (Narrative) (Details) - Stock Compensation Plan [Member] - $ / shares	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	863,025	651,900	810,100	646,900
Weighted average price of anti-dilutive options outstanding	$ 21.94	$ 26.16	$ 22.81	$ 26.25
Exercise of stock options (shares)	55		7,571	7,571

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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Number of share options (or share units) exercised during the current period.

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