Stock Options, Restricted Stock and Restricted Stock Units (Details Textual) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended	1 Months Ended
Mar. 31, 2015	Feb. 28, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum term of the awards granted under the Plan	10 years
Stock-based compensation cost which has not yet been recognized	$ 30.8
Stock-based compensation cost recognized period, in months	40 months
Restricted stock awarded subject to performance condition	426,000
Tax shortfall related to share-based payments	$ 1.6
Exercises, Number of shares	0
Vested, Number of shares	0
Board of Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares approved for grants		71,991
Vesting percentage		100.00%
Vesting date		Feb. 28, 2019
Closing price of stock on date of stock grant		$ 70.15

Closing price of stock on date of stock grant.

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- Definition

Excess tax shortfall resulting from increases in the entity's income taxes that arise when compensation cost (from non-qualified share-based compensation) recognized on the entity's tax return does not exceed compensation cot from equity based compensation recognized in financial statements. Excess tax benefits resulting from decreases in the entity's income taxes that arise when compensation cost (from non-qualified share-based compensation) recognized on the entity's tax return exceeds compensation cost from equity-based compensation recognized in financial statements.

+ References

No definition available.

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- Definition

Maximum term of the awards granted under the plan.

+ References

No definition available.

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- Definition

Restricted stock awarded subject to performance condition.

+ References

No definition available.

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- Definition

Share based compensation arrangement by share based payment award award vesting date.

+ References

No definition available.

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- Definition

Unrecognized cost of unvested share-based compensation awards.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (i)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

Percentage of vesting of share-based compensation awards.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)(1)

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- Definition

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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-Paragraph 2

-Subparagraph (c)(2)(iii)(2)

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- Definition

The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

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-Topic 718

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- Definition

Number of share options (or share units) exercised during the current period.

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-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

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-Publisher SEC

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