Partners' Capital and Distributions (Quarterly Distributions Of Available Cash) (Details) (USD $)	3 Months Ended
Dec. 31, 2012	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2009
Partners’ Capital and Distributions [Abstract]
Distribution date	Feb. 14, 2013	Nov. 14, 2012	Aug. 14, 2012	May 14, 2012	Feb. 13, 2012	Nov. 14, 2011	Aug. 12, 2011	May 13, 2011	Feb. 14, 2011
Cash distribution per unit	$ 0.46	$ 0.460	$ 0.460	$ 0.460	$ 0.460	$ 0.455	$ 0.450	$ 0.445	$ 0.445

Cash dividends declared or paid to each outstanding limited partnership unit during the reporting period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section S99

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6959260&loc=d3e187171-122770

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 4

-Section F

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