Change in Accounting Principle (Details) (USD $)	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Balance Sheet Disclosures
Accounts receivable crude oil resales	$ 25,702,000		$ 5,166,000
Total current assets	3,705,692,000		3,920,746,000
Total assets	9,382,532,000		9,576,243,000
Accounts payable	1,096,216,000		1,504,694,000
Total current liabilities	1,561,685,000		1,890,683,000
Total liabilities and equity	9,382,532,000		9,576,243,000
Receivables, reported as a reduction of accounts payable	673,800,000
Statement of Cash Flows Disclosures
Increase (decrease) in accounts receivable	103,674,000	(38,017,000)
Increase (decrease) in accounts payable	(418,937,000)	160,760,000
As Originally Reported [Member]
Balance Sheet Disclosures
Accounts receivable crude oil resales			743,544,000
Total current assets			4,659,124,000
Total assets			10,314,621,000
Accounts payable			2,243,072,000
Total current liabilities			2,629,061,000
Total liabilities and equity			10,314,621,000
Statement of Cash Flows Disclosures
Increase (decrease) in accounts receivable		(10,411,000)
Increase (decrease) in accounts payable		133,154,000
Effect of Change [Member]
Balance Sheet Disclosures
Accounts receivable crude oil resales			(738,378,000)
Total current assets			(738,378,000)
Total assets			(738,378,000)
Accounts payable			(738,378,000)
Total current liabilities			(738,378,000)
Total liabilities and equity			(738,378,000)
Statement of Cash Flows Disclosures
Increase (decrease) in accounts receivable		(27,606,000)
Increase (decrease) in accounts payable		$ 27,606,000