Subsequent Events (Details) (USD $)	Dec. 31, 2011	Dec. 31, 2010	Jul. 31, 2010 DG Marine [Member]	Dec. 31, 2011 Poseidon Oil Pipeline Company, L.L.C. [Member] Mi	Dec. 31, 2011 Odyssey Pipeline L.L.C. [Member] Mi	Dec. 31, 2011 Eugene Island Pipeline System [Member] In Mi	Feb. 01, 2012 Senior Unsecured Notes [Member]	Dec. 31, 2011 Senior Unsecured Notes [Member]	Dec. 31, 2011 Maximum [Member] Poseidon Oil Pipeline Company, L.L.C. [Member] In	Dec. 31, 2011 Maximum [Member] Odyssey Pipeline L.L.C. [Member] In	Dec. 31, 2011 Minimum [Member] Poseidon Oil Pipeline Company, L.L.C. [Member] In	Dec. 31, 2011 Minimum [Member] Odyssey Pipeline L.L.C. [Member] In	Dec. 31, 2011 Gulf Of Mexico Crude Oil Pipelines [Member]
Pipeline diameter, in inches						20			24	20	16	12
Pipeline length, in miles				367	120	183
Ownership percentage			49.00%	28.00%	29.00%	23.00%
Purchase price of acquired entity													$ 205,900,000
Crude oil line fill included in purchase price	26,000,000
Pipeline capacity, barrels per day		500,000		400,000	300,000	200,000
Debt Instrument, Face Amount							$ 100,000,000
Debt instrument, stated rate								7.875%
Debt instrument, effective interest rate								7.682%
Debt instrument, percentage of face value							101.00%