Debt (Narrative) (Details) (USD $)	12 Months Ended												12 Months Ended								12 Months Ended					12 Months Ended				12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 Letter Of Credit [Member]	Dec. 31, 2011 Senior Secured Credit Facility [Member]	Aug. 31, 2011 Senior Secured Credit Facility [Member]	Dec. 31, 2011 Senior Secured Credit Facility [Member] Crude Oil And Petroleum Products Inventory [Member]	Aug. 31, 2011 Senior Secured Credit Facility [Member] Crude Oil And Petroleum Products Inventory [Member]	Dec. 31, 2011 Senior Secured Credit Facility [Member] Letter Of Credit [Member]	Aug. 31, 2011 Senior Secured Credit Facility [Member] Accordion [Member]	Feb. 01, 2012 Senior Unsecured Notes [Member]	Dec. 31, 2011 Senior Unsecured Notes [Member]	Dec. 31, 2010 Senior Unsecured Notes [Member]	Dec. 31, 2011 7.875% Senior Unsecured Notes [Member]	Dec. 31, 2010 7.875% Senior Unsecured Notes [Member]	Nov. 30, 2010 7.875% Senior Unsecured Notes [Member]	Dec. 31, 2011 Federal Funds Effective Rate [Member]	Dec. 31, 2011 Eurodollar Rate [Member]	Dec. 31, 2011 Applicable Margin [Member]	Nov. 30, 2010 CHOPS [Member]	Jul. 31, 2010 DG Marine [Member]	Dec. 31, 2011 Maximum [Member]	Dec. 31, 2011 Maximum [Member] Letter Of Credit [Member]	Dec. 31, 2011 Maximum [Member] Senior Secured Credit Facility [Member] Letter Of Credit [Member]	Aug. 19, 2011 Maximum [Member] Alternate Base Rate [Member]	Aug. 19, 2011 Maximum [Member] Eurodollar Rate [Member]	Dec. 31, 2011 Minimum [Member]	Dec. 31, 2011 Minimum [Member] Letter Of Credit [Member]	Aug. 19, 2011 Minimum [Member] Alternate Base Rate [Member]	Aug. 19, 2011 Minimum [Member] Eurodollar Rate [Member]	Dec. 31, 2011 During Acquisition Period [Member] Senior Secured Credit Facility [Member]	Aug. 31, 2011 Amended Facility [Member] Senior Secured Credit Facility [Member]	Aug. 31, 2011 Amended Facility [Member] Senior Secured Credit Facility [Member] Crude Oil And Petroleum Products Inventory [Member]	Aug. 31, 2011 Amended Facility [Member] Senior Secured Credit Facility [Member] Accordion [Member]
Debt Instrument [Line Items]
Fair value of senior unsecured notes											$ 253,100,000	$ 250,300,000
Senior secured credit facility, maximum borrowing capacity					525,000,000		75,000,000		125,000,000																						775,000,000	125,000,000	225,000,000
Line of credit facility, aggregate maximum borrowing capacity					1,000,000,000
Total amount available for borrowings, remaining borrowing capacity				356,700,000
Senior secured credit facility, amount outstanding				409,300,000		69,600,000
Letters of credit, outstanding amount								9,000,000															100,000,000
Maturity date of debt		Jun. 30, 2015												Dec. 15, 2018
Interest rate spreads senior secured credit facility																0.50%	2.50%	1.50%						2.00%	3.00%			1.00%	2.00%
Letter of credit, fee percentage			2.50%																			3.50%					2.50%
Commitment fee percentage	0.375%																				0.50%					0.375%
Financing costs deferred																										775.000
Debt instrument covenant, requirement leverage ratio				5.00																										5.50
Debt instrument covenant, requirement senior secured leverage ratio				3.75																										4.25
Debt instrument covenant, requirement interest coverage ratio				2.75																										3.00
Debt instrument, principal amount										$ 100,000,000					$ 250,000,000
Debt instrument, stated rate											7.875%		7.875%		7.875%
Percentage of equity interest																			50.00%	49.00%
Maximum percentage of principal, early debt redemption													35.00%
Percentage of the redeemable value of debt on Face amount													107.875%
Earliest debt redemption date													December 15, 2013