Significant Customers (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenue, Major Customer [Line Items]
Number of significant customers	2
Concentration risk, precentage of total revenues	10.00%
Export sales revenues percentage	10.00%
Sinclair Oil Company [Member]
Revenue, Major Customer [Line Items]
Concentration risk, precentage of total revenues	11.00%	10.00%	13.00%
Revenue for reportable segment	$ 2,134.3	$ 2,106.6	$ 2,035.1
Export sales revenues percentage	11.00%	10.00%	13.00%
Shell Oil Company [Member]
Revenue, Major Customer [Line Items]
Concentration risk, precentage of total revenues	9.00%	12.00%	10.00%
Revenue for reportable segment	1,830.5	2,323.6	1,540.6
Export sales revenues percentage	9.00%	12.00%	10.00%
Affiliate Of PEMEX [Member]
Revenue, Major Customer [Line Items]
Concentration risk, precentage of total revenues	2.00%	2.00%	2.00%
Revenue for reportable segment	$ 310.0	$ 429.4	$ 370.0
Export sales revenues percentage	2.00%	2.00%	2.00%