Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016
Basic and Diluted Earnings per Share [Line Items]
Net income	$ 19,936	$ 22,427
Weighted-average common shares outstanding (in shares)	25,443,101	25,209,888
Weighted-average common shares for EPS calculation (in shares)	25,854,181	25,596,437
Basic earnings per common share (in dollars per share)	$ 0.78	$ 0.89
Diluted earnings per common share (in dollars per share)	$ 0.77	$ 0.88
Awards excluded from diluted earnings per share calculation (in shares)	0	180,912
Restricted Stock Unit Awards
Basic and Diluted Earnings per Share [Line Items]
Add dilutive effect of share-based awards outstanding (in shares)	248,717	154,742
Stock Options
Basic and Diluted Earnings per Share [Line Items]
Add dilutive effect of share-based awards outstanding (in shares)	162,363	231,807

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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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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