Equity-Based Compensation Plans Summary of Status of Outstanding Performance Share Awards (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares [Roll Forward]
Beginning Balance	0
Granted	163,137
Forfeited	(12,557)
Ending Balance	150,580
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Beginning Balance	$ 0.00
Granted	$ 66.85
Forfeited	$ 66.97
Ending Balance	$ 66.84
Aggregate intrinsic value
Aggregate intrinsic value	$ 258
Performance shares
Number of share
Ending Balance	300,864	259,841	392,655
Granted	54,379	124,513	150,865
Settled	0	(246,592)	(499,680)
Forfeited	(13,356)	(10,735)	(8,068)
Beginning Balance	259,841	392,655	749,538
Weighted Average Grant Date Fair Value
Beginning Balance	$ 50.87	$ 44.67	$ 19.52
Granted	$ 105.08	$ 63.46	$ 40.24
Settled	$ 0.00	$ 47.19	$ 5.65
Forfeited	$ 71.03	$ 54.87	$ 42.15
Ending Balance	$ 59.77	$ 50.87	$ 44.67
Aggregate intrinsic value
Aggregate intrinsic value	$ 20,624	$ 13,642	$ 15,376

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Intrinsic value of equity-based compensation awards not vested. Excludes stock and unit options.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)(iv)(3)

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

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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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Gross number of share options (or share units) granted during the period.

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Number of non-vested options outstanding.

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Number of non-vested options forfeited.

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Weighted average grant-date fair value of non-vested options forfeited.

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Weighted average grant-date fair value of non-vested options outstanding.

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of fully vested and expected to vest options that are exercisable.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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