Long-Term Equity Compensation (Summary of Restricted Stock Units and Performance Stock Units) (Details) (USD $)	12 Months Ended
Dec. 31, 2012
Long Term Equity Compensation [Abstract]
Outstanding beginning balance, Number of Restricted Stock Units and Performance Share Units	2,210,306
Granted, Number of Restricted Stock Units and Performance Share Units	1,084,532
Vested, Number of Restricted Stock Units and Performance Share Units	(1,263,567)
Forfeited, Number of Restricted Stock Units and Performance Share Units	(93,601)
Outstanding ending balance, Number of Restricted Stock Units and Performance Share Units	1,937,670
Outstanding beginning balance, Weighted Average Grant-Date Fair Value	$ 26.56
Granted, Weighted Average Grant-Date Fair Value	$ 38.22
Vested,Weighted Average Grant-Date Fair Value	$ 26.46
Forfeited, Weighted Average Grant-Date Fair Value	$ 27.57
Outstanding ending balance, Weighted Average Grant-Date Fair Value	$ 33.13
Outstanding beginning balance, Weighted Average Purchase Price	$ 0.001
Granted, Weighted Average Purchase Price	$ 0.001
Vested, Weighted Average Purchase Price	$ 0.001
Forfeited, Weighted Average Purchase Price	$ 0.001
Outstanding ending balance, Weighted Average Purchase Price	$ 0.001
Outstanding, Weighted Average Remaining Contractual Term (Years)	1 year 8 months 12 days
Outstanding, Aggregated Intrinsic Value	$ 47,084,016
Expected to vest, Number of Restricted Stock Units and Performance Share Units	1,528,324
Expected to vest, Weighted Average Grant-Date Fair Value	33.54
Expected to vest, Weighted Average Purchase Price	$ 0.001
Expected to vest, Weighted Average Remaining Contractual Term (Years)	1 year 8 months 22 days
Expected to vest, Aggregate Intrinsic Value	$ 37,137,207

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Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited In Period, Weighted Average Purchase Price

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Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Purchase Price

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The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

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Weighted average remaining contractual term for equity-based awards excluding options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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