Debt (Narrative) (Details) (USD $)								3 Months Ended
	Nov. 18, 2010	Mar. 31, 2014 7.875% Senior Unsecured Notes [Member]	Dec. 31, 2013 7.875% Senior Unsecured Notes [Member]	Feb. 01, 2012 7.875% Senior Unsecured Notes [Member]	Feb. 01, 2012 Unsecured Debt [Member]	Mar. 31, 2014 Senior Secured Credit Facility [Member]	Mar. 31, 2014 Senior Secured Credit Facility [Member] Letters Of Credit [Member]	Mar. 31, 2014 Five Point Seventy Five Percentage Senior Unsecured Notes [Member]	Dec. 31, 2013 Five Point Seventy Five Percentage Senior Unsecured Notes [Member]	Feb. 08, 2013 Five Point Seventy Five Percentage Senior Unsecured Notes [Member]	Mar. 31, 2014 Amended Facility [Member]	Mar. 31, 2014 Maximum [Member] Senior Secured Credit Facility [Member] Letters Of Credit [Member]	Mar. 31, 2014 Petroleum Products [Member] Senior Secured Credit Facility [Member]
Debt Instrument [Line Items]
Credit facility, amount outstanding						$ 640,500,000							$ 71,600,000
Credit facility, maximum borrowing capacity											1,000,000,000
Letters of credit, outstanding amount							12,400,000					100,000,000
Credit facility and senior unsecured notes, maturity dates								Feb. 15, 2021
Total amount available for borrowings under credit facility						347,100,000
Senior unsecured notes, principal amount	250,000,000			100,000,000	350,000,000					350,000,000
Senior unsecured notes, stated rate	7.875%	7.875%	7.875%					5.75%	5.75%	5.75%
Senior unsecured notes, percentage of face value					101.00%
Debt Instrument, Interest Rate, Effective Percentage					7.682%
Debt Instrument, Unamortized Premium		$ 740,000	$ 772,000
Maximum Percentage Of Principal, Early Debt Redemption								35.00%
Redemption premium for notes								105.75%