Acquisitions (Proforma Financial Results) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Prize [Member]
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Total Revenue, Proforma	$ 64,969	$ 72,815	$ 205,081	$ 221,574
Operating income, Proforma	8,565	14,292	33,314	58,349
Net income (loss), Proforma	$ (45,007)	$ 107,530	$ 51,983	$ 97,577
Limited Partners-Affiliated - Common [Member]
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Unitholders' (basic) (in dollars per unit)	$ (1.25)	$ 1.45	$ 0.49	$ 1.07
Limited Partners-Affiliated - Common [Member] | Prize [Member]
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Unitholders' (basic) (in dollars per unit), Proforma	$ (1.25)	$ 1.21	$ 0.54	$ 1.08
Unitholders' (diluted) (in dollars per unit), Proforma	$ (1.25)	$ 1.21	$ 0.54	$ 1.08
Limited Partners-Affiliated - Subordinated [Member]
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Unitholders' (basic) (in dollars per unit)	$ (1.26)	$ 1.45	$ 0.33	$ 1.07
Limited Partners-Affiliated - Subordinated [Member] | Prize [Member]
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Unitholders' (basic) (in dollars per unit), Proforma	$ (1.26)	$ 1.21	$ 0.53	$ 1.08
Unitholders' (diluted) (in dollars per unit), Proforma	$ (1.26)	$ 1.21	$ 0.53	$ 1.08