Earnings Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
Mar. 31, 2014	Mar. 31, 2013
Earnings Per Share [Abstract]
Income from continuing operations for calculating basic and diluted earnings per share	$ 22,954	$ 20,180
Income (loss) from discontinued operations	(272)	84
Net income	$ 22,682	$ 20,264
Weighted-average common shares for calculating basic earnings per share	28,952	29,313
Stock options and nonvested awards	390	642
Weighted-average common shares for calculating diluted earnings per share	29,342	29,955
Income from continuing operations (basic) (in dollars per share)	$ 0.79	$ 0.69
Income from discontinued operations (basic) (in dollars per share)	$ (0.01)	$ 0.00
Net income per basic share (in dollars per share)	$ 0.78	$ 0.69
Income from continuing operations (diluted) (in dollars per share)	$ 0.78	$ 0.68
Income from discontinued operations (diluted) (in dollars per share)	$ (0.01)	$ 0.00
Net income per diluted share (in dollars per share)	$ 0.77	$ 0.68

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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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This element represents the income or loss from continuing operations attributable to the economic entity which may also be defined as revenue less expenses and taxes from ongoing operations before extraordinary items, and noncontrolling interest.

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The amount of net income (loss) from continuing operations per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) derived from continuing operations during 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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Amount of income (loss) from a disposal group, net of income tax before extraordinary items allocable to noncontrolling interests. Includes, net of tax, income (loss) from operations during the phase-out period, gain (loss) on disposal, provision (or any reversals of earlier provisions) for loss on disposal, and adjustments of a prior period gain (loss) on disposal.

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Per basic share amount, after tax, of income (loss) from the day-to-day business activities of the discontinued operation and gain (loss) from the disposal of the discontinued operation.

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Per diluted share amount, after tax, of income (loss) from the day-to-day business activities of the discontinued operation and gain (loss) from the disposal of the discontinued operation.

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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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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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