Long-Term Debt (Partnership's Long-Term Debt) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Long-Term Debt Disclosure [Abstract]
Senior notes	$ 1,354,915	$ 1,355,147
Revolving loans	250,000	332,000
Total	1,604,915	1,687,147
Less: current portion	0	0
Long-term debt	1,604,915	1,687,147
Total credit facility limit	900,000	900,000
Availability under revolving loans	(250,000)	(332,000)
Letters of credit	(11,500)	(19,000)
Total available	$ 638,500	$ 549,000