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Cash Distributions and Net Income (Loss) per Common Unit - Schedule of Partner Distributions Made (Details) (USD $)
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0 Months Ended | 1 Months Ended | 3 Months Ended | 12 Months Ended | ||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
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Mar. 26, 2007
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Sep. 30, 2012
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May 31, 2012
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Sep. 30, 2011
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Sep. 30, 2012
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Jun. 30, 2012
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Mar. 31, 2012
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Dec. 31, 2011
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Sep. 30, 2011
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Jun. 30, 2011
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Mar. 31, 2011
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Dec. 31, 2010
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Sep. 30, 2010
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Jun. 30, 2010
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Mar. 31, 2010
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Dec. 31, 2009
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Dec. 31, 2012
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Dec. 31, 2011
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| Distribution Made to Member or Limited Partner [Line Items] | ||||||||||||||||||
| Number of days after quarter end distribution is paid | $ 45 | |||||||||||||||||
| Date paid | Nov. 14, 2012 | Aug. 13, 2012 | May 14, 2012 | Feb. 12, 2012 | Nov. 14, 2011 | Aug. 12, 2011 | May 13, 2011 | Feb. 11, 2011 | Nov. 12, 2010 | Aug. 13, 2010 | May 14, 2010 | Feb. 12, 2010 | ||||||
| Total distribution | 333,453,000 | 313,619,000 | ||||||||||||||||
| Partner units issued and sold | 133,300,000 | |||||||||||||||||
| Partner units issued and sold, unit price ($US$ per unit) | $ 21.00 | $ 15.00 | ||||||||||||||||
| Proceeds from sale of partnership units | 194,000,000 | 2,000,000,000 | 60,000,000 | 11,100,000 | 9,000,000 | |||||||||||||
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Common Units
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| Distribution Made to Member or Limited Partner [Line Items] | ||||||||||||||||||
| Distribution per unit | 0.425 | 0.425 | 0.425 | 0.425 | 0.425 | 0.425 | 0.425 | 0.425 | 0.425 | 0.425 | 0.425 | 0.425 | ||||||
| Total distribution | 16,783,000 | 13,383,000 | 13,323,000 | 13,176,000 | 13,176,000 | 11,446,000 | 11,335,000 | 11,229,000 | 11,227,000 | 11,227,000 | 11,227,000 | 11,227,000 | ||||||
| Partner units issued and sold, unit price ($US$ per unit) | $ 25.07 | |||||||||||||||||
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Class B Unit [Member]
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| Distribution Made to Member or Limited Partner [Line Items] | ||||||||||||||||||
| Total distribution | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | ||||||
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Subordinated Units
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| Distribution Made to Member or Limited Partner [Line Items] | ||||||||||||||||||
| Distribution per unit | 0.000 | 0.000 | 0.000 | 0.000 | 0.000 | 0.000 | 0.000 | 0.000 | 0.425 | 0.425 | ||||||||
| Total distribution | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 57,538,000 | 57,538,000 | ||||||||
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General Partner [Member]
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| Distribution Made to Member or Limited Partner [Line Items] | ||||||||||||||||||
| Total distribution | 342,000 | 273,000 | 272,000 | 269,000 | 269,000 | 234,000 | 231,000 | 229,000 | 229,000 | 229,000 | 1,403,000 | 1,403,000 | ||||||