Long-Term Debt (Partnership's Long-Term Debt) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Long-Term Debt Disclosure [Abstract]
Senior notes	$ 1,265,429	$ 1,355,147
Revolving loans	695,000	332,000
Total	1,960,429	1,687,147
Less: current portion	0	0
Long-term debt	1,960,429	1,687,147
Total credit facility limit	1,150,000	900,000
Revolving loans	(695,000)	(332,000)
Letters of credit	(8,600)	(19,000)
Total available	$ 446,400	$ 549,000