Acquisitions (Proforma Financial Results) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Prize [Member]
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Total Revenue, Proforma	$ 64,258	$ 77,285	$ 140,112	$ 148,758
Gain from operations, Proforma	6,220	23,586	24,749	44,057
Net income (loss), Proforma	$ 99,929	$ 33,380	$ 96,990	$ (9,954)
Limited Partners-Affiliated - Common [Member]
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Unitholders' (basic) (in dollars per unit)	$ 2.15	$ 0.44	$ 1.92	$ (0.38)
Limited Partners-Affiliated - Common [Member] | Prize [Member]
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Unitholders' (basic) (in dollars per unit), Proforma	$ 2.16	$ 0.45	$ 2.05	$ (0.13)
Unitholders' (diluted) (in dollars per unit), Proforma	$ 1.68	$ 0.45	$ 1.69	$ (0.13)
Limited Partners-Affiliated - Subordinated [Member]
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Unitholders' (basic) (in dollars per unit)	$ 2.12	$ 0.44	$ 1.76	$ (0.38)
Limited Partners-Affiliated - Subordinated [Member] | Prize [Member]
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Unitholders' (basic) (in dollars per unit), Proforma	$ 2.14	$ 0.45	$ 1.88	$ (0.13)
Unitholders' (diluted) (in dollars per unit), Proforma	$ 1.67	$ 0.45	$ 1.62	$ (0.13)