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Stock-based Compensation and Awards (Details 4) (Phantom Units [Member], USD $)	12 Months Ended
	Dec. 31, 2011
Phantom Units [Member]
Schedule of phantom unit activity
Granted, Shares	49,082
Vested Units	(67,026)
Cancelled, Shares	(5,326)
Beginning balance, Shares	98,537
Ending balance, Shares	75,267
Granted Weighted average grant date fair value per unit	$ 24.70
Vested Weighted average grant date fair value per unit	$ 20.47
Cancelled, Weighted average grant date fair value per share	$ 22.56
Ending balance, Weighted average grant date fair value per share	$ 21.45
Beginning balance, Weighted average grant date fair value per share	$ 19.23

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- Definition

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

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The 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 during the reporting period as a result of the occurrence of a terminating event specified in the contractual agreement of the plan.

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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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