Earnings Per Share (Schedule of Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share [Abstract]
Earnings of basic earnings per common share	$ 7,865	$ 15,929
Income of effect of dilutive stock options, restricted stock, and stock appreciation rights (SARs)	0	0
Earnings of diluted income per common share	$ 7,865	$ 15,929
Weighted shares of basic earnings per common share	51,730	50,293
Weighted shares of effect of dilutive stock options, restricted stock, and stock appreciation rights (SARs)	542	568
Weighted shares of diluted earnings per common share	52,272	50,861
Per-Share amount of basic earnings per common share	$ 0.15	$ 0.32
Per-Share amount of effect of dilutive stock options, restricted stock, and stock appreciation rights (SARs)	0.00	(0.01)
Per-Share amount of diluted earnings per common share	$ 0.15	$ 0.31

Incremental Per Share Effect Of Dilutive Income Changes Over Dilutive Share Changes

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Amount of increase (decrease) to net income used for calculating diluted earnings per share (EPS), resulting from the assumed exercise stock options, restrictive stock units (RSUs), convertible preferred stock of an employee stock ownership plan (ESOP), and other dilutive convertible securities.

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The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities, and addition from assumption of issuance of common shares for dilutive potential common shares; of income (loss) available to common shareholders.

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The sum of dilutive potential common shares or units used in the calculation of the diluted per-share or per-unit computation.

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The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

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Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

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