Earnings (Loss) Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net (loss) earnings	$ (12,599)	$ 6,181	$ (28,171)	$ 41,188
Weighted average shares outstanding	53,306	53,155	53,272	53,111
Effect of dilutive stock awards	0	299	0	281
Weighted-average dilutive shares	53,306	53,454	53,272	53,392
Basic (loss) earnings per common share	$ (0.24)	$ 0.12	$ (0.53)	$ 0.78
Diluted (loss) earnings per common share	$ (0.24)	$ 0.12	$ (0.53)	$ 0.77
Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive stock options	1,419	814	1,419	814
Employee Stock Option [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive stock options	3,103	3,185	3,103	2,618

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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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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