Partnership Operations, Organization and Basis of Presentation (Details)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010 Common units [Member]	Dec. 31, 2011 Duncan Merger [Member]	Dec. 31, 2011 Duncan Merger [Member] Common units [Member]	Dec. 31, 2010 Holdings Merger [Member]	Dec. 31, 2010 Holdings Merger [Member] Common units [Member]
Partnership Operations, Organization and Basis of Presentation [Abstract]
Number of reportable segments	5
Limited partners ownership interest (in hundredths)	100.00%
Mergers [Line Items]
Common unit exchange ratio in connection with merger				1.01	1.01	1.5	1.5
Common units issued in connection with merger (in units)					24,277,310		208,813,454
Common units cancelled immediately after merger (in units)			21,563,177				21,563,177
General partner ownership interest cancelled as a result of merger (in hundredths)						2.00%
Number of years a privately held affiliate agreed to waive regular quarterly cash distributions (in years)						5
Number of Designated Units (in units)	26,130,000	30,610,000
Number of Designated Units to be excluded from distributions during 2013	23,700,000
Number of Designated Units to be excluded from distributions during 2014	22,560,000
Number of Designated Units to be excluded from distributions during 2015	17,690,000