Partners' Capital and Distributions Narrative (Details) (USD $)	1 Months Ended	6 Months Ended		1 Months Ended	3 Months Ended
	May 31, 2012	Jun. 30, 2012	Jun. 30, 2011	May 31, 2012 Common Unit Public Offering [Member]	Mar. 31, 2012 Common Unit Public Offering [Member]
Capital Unit [Line Items]
Equity Distribution Agreement maximum aggregate value of common units to be sold		$ 200,000,000
Partners' capital account, units, sold in public offering					12,650,000
Common issuance price per unit					$ 24.47
Common unit offering, net of costs		296,817,000	203,917,000
Senior note redeemable portion				35.00%
Repayments of long-term debt	$ 87,500,000	$ 87,500,000	$ 0