Partners' Capital And Distributions (Narrative) (Details) (USD $) In Millions, except Share data, unless otherwise specified	0 Months Ended	3 Months Ended	9 Months Ended								9 Months Ended					3 Months Ended		9 Months Ended
	Sep. 16, 2013	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2012	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2013 Waiver Units Class 1 [Member]	Sep. 30, 2013 Waiver Units Class 3 [Member]	Sep. 30, 2013 Waiver Units Class 4 [Member]	Sep. 30, 2013 Class A [Member]	Sep. 30, 2013 Class B [Member]	Sep. 30, 2013 Waiver Units [Member]	May 15, 2013 Waiver Units [Member]	Sep. 30, 2013 Class Two [Member]	Sep. 30, 2013 Class Three [Member]	Sep. 30, 2013 Class Four [Member]	Sep. 30, 2013 Waiver Units Class2 [Member]
Partners Capital And Distributions [Line Items]
Common units, issued	5,750,000	88,690,985	88,690,985				81,202,752
Sale of Stock, Price Per Share	$ 47.51
Partners' Capital Account, Public Sale of Units Net of Offering Costs	$ 263.6
Issuance of common units			5,750,000	5,750,000
Common units, outstanding		88,690,985	88,690,985	81,203,000			81,202,752			71,965,000				88,650,988	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																			0.49	0.52
Distribution paid per common unit		$ 0.5225	$ 0.5225	$ 0.4725	$ 0.5100	$ 0.4975	$ 0.4850	$ 0.4600	$ 0.4500								$ 0.4975
Waiver Units Class 3 Convertible Date		May 15, 2013
Waiver units outstanding													1,738,000