Earnings Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Earnings Per Share [Abstract]
Income from continuing operations for calculating basic and diluted earnings per share	$ 16,788	$ 22,954
Loss from discontinued operations	0	(272)
Net income	$ 16,788us-gaap_NetIncomeLoss	$ 22,682us-gaap_NetIncomeLoss
Weighted-average common shares for calculating basic earnings per share	28,402	28,952
Stock options and nonvested awards	218	390
Weighted-average common shares for calculating diluted earnings per share	28,620	29,342
Basic earnings per share:
Income from continuing operations (in dollars per share)	$ 0.59	$ 0.79
Income from discontinued operations (in dollars per share)	$ 0.00	$ (0.01)
Net income per basic share (in dollars per share)	$ 0.59us-gaap_EarningsPerShareBasic	$ 0.78us-gaap_EarningsPerShareBasic
Diluted earnings per share:
Income from continuing operations (in dollars per share)	$ 0.59	$ 0.78
Income from discontinued operations (in dollars per share)	$ 0.00	$ (0.01)
Net income per diluted share (in dollars per share)	$ 0.59us-gaap_EarningsPerShareDiluted	$ 0.77us-gaap_EarningsPerShareDiluted

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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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