Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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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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- 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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Unit-Based Compensation (Narrative) (Details) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended	3 Months Ended		9 Months Ended
	Jul. 31, 2012	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Common Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common unit awards authorized		1,800,000		1,800,000
Service Unit [Member] \| Restricted Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted common units awarded to employees	392,149			428,000
Price per restricted common unit awarded to employees	$ 18.19
Compensation expense		$ 1.4	$ 0.4	$ 2.2	$ 1.0
Unvested units, December 31, 2011				271,000
Restricted unit awards outstanding		645,563		645,563
Restricted unit awards unamortized grant date fair value		$ 11.9		$ 11.9
Weighted average amortization period of grant date fair value, years				3 years
Performance Unit [Member] \| Restricted Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted common units awarded to employees				121,000
Unvested units, December 31, 2011
Restricted unit awards outstanding		121,000		121,000