Transactions With Related Parties (Narrative) (Details) (USD $) In Millions, unless otherwise specified									12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Nov. 30, 2010	Dec. 31, 2009	Dec. 31, 2010 Compensation Recognized For Executive Management Team [Member]	Dec. 31, 2009 Compensation Recognized For Executive Management Team [Member]	Dec. 31, 2011 Robertson Group [Member]	Dec. 31, 2010 Robertson Group [Member]	Dec. 31, 2011 Sandhill [Member]	Dec. 31, 2010 Sandhill [Member]	Jul. 29, 2010 DG Marine [Member]
Related Party Transaction [Line Items]
Percentage of equity interest acquired											51.00%
Due from related parties							$ 1.9	$ 1.4	$ 0.2	$ 0.2
Due to related parties	0.3						0.1	0.2
Loan held by related party									1.7	2.2
Percentage of obligation guaranteed									50.00%
Guaranty obligation									0.9	1.1
General partner made capital contributions		$ 2.5	$ 2.5	$ 0.1	$ 76.9	$ 14.1