Debt (Narrative) (Details) (USD $)	12 Months Ended								12 Months Ended		12 Months Ended								12 Months Ended					12 Months Ended
	Dec. 31, 2012	Dec. 31, 2012 Letter Of Credit [Member]	Dec. 31, 2012 Senior Secured Credit Facility [Member]	Jul. 25, 2012 Senior Secured Credit Facility [Member]	Dec. 31, 2012 Senior Secured Credit Facility [Member] Crude Oil And Petroleum Products Inventory [Member]	Jul. 25, 2012 Senior Secured Credit Facility [Member] Crude Oil And Petroleum Products Inventory [Member]	Dec. 31, 2012 Senior Secured Credit Facility [Member] Letter Of Credit [Member]	Jul. 25, 2012 Senior Secured Credit Facility [Member] Accordion [Member]	Dec. 31, 2012 Senior Unsecured Notes [Member]	Feb. 01, 2012 Senior Unsecured Notes [Member]	Dec. 31, 2012 7.875% Senior Unsecured Notes [Member]	Dec. 31, 2010 7.875% Senior Unsecured Notes [Member]	Feb. 01, 2012 7.875% Senior Unsecured Notes [Member]	Nov. 30, 2010 7.875% Senior Unsecured Notes [Member]	Dec. 31, 2012 Federal Funds Effective Rate [Member]	Dec. 31, 2012 Eurodollar Rate [Member]	Dec. 31, 2012 Applicable Margin [Member]	Nov. 30, 2010 CHOPS [Member]	Dec. 31, 2012 Maximum [Member]	Dec. 31, 2011 Maximum [Member] Senior Secured Credit Facility [Member]	Dec. 31, 2012 Maximum [Member] Senior Secured Credit Facility [Member] Letter Of Credit [Member]	Dec. 31, 2012 Maximum [Member] Federal Funds Effective Rate [Member]	Dec. 31, 2012 Maximum [Member] LIBOR Rate [Member]	Dec. 31, 2012 Maximum [Member] Alternate Base Rate [Member]	Dec. 31, 2012 Maximum [Member] Eurodollar Rate [Member]	Dec. 31, 2012 Minimum [Member]	Dec. 31, 2011 Minimum [Member] Senior Secured Credit Facility [Member]	Dec. 31, 2012 Minimum [Member] Alternate Base Rate [Member]	Dec. 31, 2012 Minimum [Member] Eurodollar Rate [Member]	Dec. 31, 2011 During Acquisition Period [Member] Maximum [Member] Senior Secured Credit Facility [Member]	Dec. 31, 2011 During Acquisition Period [Member] Minimum [Member] Senior Secured Credit Facility [Member]	Jul. 25, 2012 Amended Facility [Member] Senior Secured Credit Facility [Member]	Jul. 25, 2012 Amended Facility [Member] Senior Secured Credit Facility [Member] Crude Oil And Petroleum Products Inventory [Member]	Jul. 25, 2012 Amended Facility [Member] Senior Secured Credit Facility [Member] Accordion [Member]
Debt Instrument [Line Items]
Senior secured credit facility, maximum borrowing capacity				$ 775,000,000		$ 125,000,000		$ 225,000,000																								$ 1,000,000,000	$ 150,000,000	$ 300,000,000
Line of credit facility, aggregate maximum borrowing capacity				1,300,000,000
Interest rate spreads senior secured credit facility															0.50%	2.00%	1.00%					1.00%	1.00%
Letter of credit, fee percentage		2.00%																						2.75%	1.75%			1.75%	0.75%
Commitment fee percentage	0.375%																		0.50%							0.375%
Debt instrument covenant, requirement leverage ratio																				1							5			1	5.50
Debt instrument covenant, requirement senior secured leverage ratio																				1							3.75			1	4.25
Debt instrument covenant, requirement interest coverage ratio																				1							2.75			1	3
Senior secured credit facility, amount outstanding			500,000,000		63,900,000
Letters of credit, outstanding amount							16,700,000														100,000,000
Maturity date of debt	Jul. 25, 2017								Feb. 15, 2021			Dec. 15, 2018
Total amount available for borrowings, remaining borrowing capacity			483,300,000
Debt instrument, principal amount									$ 350,000,000				$ 100,000,000	$ 250,000,000
Debt instrument, stated rate													7.875%	7.875%
Debt instrument, percentage of face value										101.00%
Debt instrument, effective interest rate										7.682%
Percentage of equity interest																		50.00%
Maximum percentage of principal, early debt redemption											35.00%
Earliest debt redemption date											Dec. 15, 2013
Percentage of the redeemable value of debt on Face amount											107.875%