Income Taxes (Details) (USD $)	3 Months Ended	6 Months Ended
Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Income tax expense (benefit)
Income tax expense	$ 27,271,000	$ 20,650,000	$ 48,990,000	$ 38,536,000
Interest and penalties expense relating to uncertain tax positions			100,000	300,000
Accrued interest and penalties relating to uncertain tax positions	$ 3,300,000		$ 3,300,000		$ 3,200,000

The sum of the current income tax expense or benefit and the deferred income tax expense or benefit pertaining to continuing operations.

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This element represents the total of accruals as of the date of the statement of financial position for interest recognized for an underpayment of income taxes computed by applying the applicable statutory rate of interest to the difference between a tax position recognized for financial reporting purposes and the amount previously taken or expected to be taken in a tax return of the entity and the amount of statutory penalties for a tax position claimed or expected to be claimed by the entity, in its tax return, that does not meet the minimum statutory threshold to avoid payment of penalties.

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- Definition

This element represents the total of interest expense recognized for an underpayment of income taxes computed by applying the applicable statutory rate of interest to the difference between a tax position recognized for financial reporting purposes and the amount previously taken or expected to be taken in a tax return of the entity and the amount of statutory penalties in the period in which the entity claims or expects to claim a tax position, in its tax return, that does not meet the minimum statutory threshold to avoid payment of penalties.

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