Share-Based Compensation (Summary of Restricted Stock Activity) (Details) - Restricted stock	9 Months Ended
Sep. 30, 2018 $ / shares shares
Number of Awards
Number of Awards, Unvested balances at beginning of period (in shares) \| shares	1,988,500
Number of Awards, Granted (in shares) \| shares	489,203
Number of Awards, Vested (in shares) \| shares	(669,577)
Number of Awards, Forfeited (in shares) \| shares	(229,214)
Number of Awards, Unvested balances at end of period (in shares) \| shares	1,578,912
Weighted-Average Grant Date Fair Value
Weighted-Average Grant Date Fair Value, Unvested balances at beginning of period (in dollars per share) \| $ / shares	$ 57.34
Weighted-Average Grant Date Fair Value, Granted (in dollars per share) \| $ / shares	81.77
Weighted-Average Grant Date Fair Value, Vested (in dollars per share) \| $ / shares	47.54
Weighted-Average Grant Date Fair Value, Forfeited (in dollars per share) \| $ / shares	63.29
Weighted-Average Grant Date Fair Value, Unvested balances at end of period (in dollars per share) \| $ / shares	$ 68.20

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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(3)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

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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.

+ References

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-Topic 718
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-Section 50
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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).

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
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-Paragraph 2
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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).

+ References

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-Publisher FASB
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- Definition

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.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
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-Paragraph 2
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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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No definition available.

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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.

+ References

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

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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- Definition

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.

+ References

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