Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
Mar. 31, 2016	Mar. 31, 2015
Basic and Diluted Earnings Per Share
Net income available to common stockholders, basic and diluted	$ 28,682	$ 27,670
Average outstanding shares - basic	76,126,251	75,206,348
Add: dilutive stock options and awards	47,166	38,611
Average outstanding shares - diluted	76,173,417	75,244,959
Basic earnings per share	$ 0.38	$ 0.37
Diluted earnings per share	$ 0.38	$ 0.37
Earnings Per Share
Stock options and restricted stock awards excluded from the diluted average outstanding share calculation	0	0

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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