Earnings per Share (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income	$ 22,837	$ 12,769	$ 31,189	$ 16,765
Weighted average basic shares outstanding (in shares)	31,862	31,709	31,824	31,698
Common stock options and restricted stock (in shares)	691	474	674	521
Weighted average shares outstanding, diluted (in shares)	32,553	32,183	32,498	32,219
Common shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from earnings per share calculation (in shares)	377	556	368	541

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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Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of share based payment arrangements using the treasury stock method.

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