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

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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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Calculation Of Numerator And Denominator In Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accounting Policies [Abstract]
Net Income									$ 137,039us-gaap_NetIncomeLoss	$ 99,153us-gaap_NetIncomeLoss	$ 104,546us-gaap_NetIncomeLoss
Weighted-average common shares outstanding									57,390,945	56,511,563	55,837,574
Stock options and nonvested stock									627,498	729,025	648,413
Denominator for net income per share									58,018,443	57,240,588	56,485,987
Earnings per common share, diluted	$ 0.43us-gaap_EarningsPerShareDiluted	$ 0.78us-gaap_EarningsPerShareDiluted	$ 0.93us-gaap_EarningsPerShareDiluted	$ 0.22us-gaap_EarningsPerShareDiluted	$ 0.20us-gaap_EarningsPerShareDiluted	$ 0.53us-gaap_EarningsPerShareDiluted	$ 0.75us-gaap_EarningsPerShareDiluted	$ 0.25us-gaap_EarningsPerShareDiluted	$ 2.36us-gaap_EarningsPerShareDiluted	$ 1.73us-gaap_EarningsPerShareDiluted	$ 1.85us-gaap_EarningsPerShareDiluted
Antidilutive securities excluded from the computation of diluted EPS									461,071	911,041	1,801,995