Summary of Significant Accounting Policies (Revision for Purchased Oil and Gas) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Sales of purchased oil and gas	$ 333,822	$ 122,093	$ 14,542
Purchased oil and gas	335,734	120,408	13,949
Other	137,386	114,175	63,071
Scenario, Previously Reported [Member]
Sales of purchased oil and gas		0	0
Financial Information, Charges and Credits, Amount Reconciling to Previously Reported Results		0	0
Other		112,490	62,478
Increase in Sales of Purchased Oil and Gas, Revision of Sales of Purchased Oil and Gas [Member] | Restatement Adjustment [Member]
Quantifying Revision in Current Year Financial Statements, Revenue Amount		122,093	14,542
Increase in Costs of Purchased Oil and Gas, Revisions of Purchased Oil and Gas [Member] | Restatement Adjustment [Member]
Quantifying Revision in Current Year Financial Statements, Expense Amount		120,408	13,949
Increase in Other Expense, Revision of Purchased Oil and Gas [Member] | Restatement Adjustment [Member]
Quantifying Revision in Current Year Financial Statements, Expense Amount		$ 1,685	$ 593