Long-Term Debt (Partnership's Long-Term Debt) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Long-Term Debt Disclosure [Abstract]
Senior notes	$ 1,265,558	$ 1,355,147
Revolving loans	515,000	332,000
Total	1,780,558	1,687,147
Less: current portion	0	0
Long-term debt	1,780,558	1,687,147
Total credit facility limit	900,000	900,000
Revolving loans	(515,000)	(332,000)
Letters of credit	(9,000)	(19,000)
Total available	$ 376,000	$ 549,000