Significant Customers (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Revenue, Major Customer [Line Items]
Number of significant customers	2
Minimum percentage of revenues from significant customers	10.00%
Sinclair Oil Company [Member]
Revenue, Major Customer [Line Items]
Export sales revenues	$ 2,106.6	$ 2,035.1	$ 1,616.0
Export sales revenues percentage	10.00%	13.00%	19.00%
Shell Oil Company [Member]
Revenue, Major Customer [Line Items]
Export sales revenues	2,323.6	1,540.6
Export sales revenues percentage	12.00%	10.00%
Affiliate Of PEMEX [Member]
Revenue, Major Customer [Line Items]
Export sales revenues	$ 429.4	$ 370.0	$ 323.2
Export sales revenues percentage	2.00%	2.00%	4.00%