Partners' Capital And Distributions (Narrative) (Details) (USD $)	3 Months Ended						6 Months Ended			6 Months Ended					3 Months Ended				6 Months Ended
	Sep. 30, 2013	Jun. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2013 Waiver Units Class 1 [Member]	Jun. 30, 2013 Waiver Units Class 3 [Member]	Jun. 30, 2013 Waiver Units Class 4 [Member]	Jun. 30, 2013 Class A [Member]	Jun. 30, 2013 Class B [Member]	Jun. 30, 2013 Waiver Units [Member]	May 15, 2013 Waiver Units [Member]	Aug. 14, 2012 Waiver Units [Member]	Feb. 14, 2012 Waiver Units [Member]	Jun. 30, 2013 Class One [Member]	Jun. 30, 2013 Class Two [Member]	Jun. 30, 2013 Class Three [Member]	Jun. 30, 2013 Class Four [Member]	Jun. 30, 2013 Waiver Units Class2 [Member]
Partners Capital And Distributions [Line Items]
Common units, issued		82,940,985	81,202,752				82,940,985
Issuance of common units							0	5,750,000
Common units, outstanding		82,940,985	81,202,752		79,465,000		82,940,985	79,465,000	71,965,000				82,900,988	39,997
Waiver units authorized										1,738,000	1,750,000	1,750,000			1,738,233								1,750,000
Conversion Feature, Minimum Distribution Coverage Ratio							1.1													1.1	1.1	1.1
Waiver units issued											1,738,000	1,738,000											1,738,000
Conversion feature threshold, quarterly distribution, minimum, per unit																			0.43	0.46	0.49	0.52
Waiver Units Class 1 Convertible Date					February 14, 2012
Distribution paid per common unit	$ 0.5100	$ 0.4975	$ 0.4850	$ 0.4725	$ 0.4600	$ 0.4500	$ 0.4975	$ 0.4600								$ 0.4975	$ 0.46	$ 0.44
Waiver Units Class 3 Convertible Date		May 15, 2013
Waiver units outstanding												1,738,000
Waiver Units Class 2 Convertible Date				August 14, 2012
Distribution Made to Member or Limited Partner, Distribution Date	Aug. 14, 2013	May 15, 2013	Feb. 14, 2013	Nov. 14, 2012	Aug. 14, 2012	May 15, 2012