Debt - Bank Credit Facilities Narrative (Details) (USD $)	3 Months Ended		3 Months Ended										3 Months Ended	12 Months Ended	3 Months Ended						3 Months Ended
	Mar. 31, 2013 bank_credit_facility	Dec. 31, 2012	Mar. 31, 2013 Begin Covenant Ratio	Mar. 31, 2013 Ending Q3 2012 Covenant Ratio	Mar. 31, 2013 Q4 2013 Covenant Ratio	Mar. 31, 2013 Q1 2013 Covenant Ratio	Mar. 31, 2013 Q2 2013 Covenant Ratio	Mar. 31, 2013 Q3 2013 Covenant Ratio	Dec. 31, 2012 Q3 2013 Covenant Ratio	Mar. 31, 2013 Maximum	Mar. 31, 2013 Maximum Senior Notes	Mar. 31, 2013 Minimum	Mar. 31, 2013 Corporate Revolving Bank Credit Facility	Dec. 31, 2012 Corporate Revolving Bank Credit Facility	Mar. 31, 2013 Corporate Revolving Bank Credit Facility Maximum	Mar. 31, 2013 Corporate Revolving Bank Credit Facility Minimum	Mar. 31, 2013 Corporate Revolving Bank Credit Facility Union Bank N.A. Maximum	Mar. 31, 2013 Corporate Revolving Bank Credit Facility Union Bank N.A. Minimum	Mar. 31, 2013 Oilfield Services Revolving Bank Credit Facility	Mar. 31, 2013 Oilfield Services Revolving Bank Credit Facility In Excess	Mar. 31, 2013 Oilfield Services Revolving Bank Credit Facility Bank Of America N.A.	Mar. 31, 2013 Oilfield Services Revolving Bank Credit Facility Bank Of America N.A. Maximum	Mar. 31, 2013 Oilfield Services Revolving Bank Credit Facility Bank Of America N.A. Minimum	Mar. 31, 2013 Midstream Revolving Bank Credit Facility
Long-Term Debt Instrument [Line Items]
Number of revolving bank credit facilities used	2
Borrowing Capacity													$ 4,000,000,000						$ 500,000,000
Interest Rate In Addition To Federal Funds Rate														0.50%					0.50%
Debt Instrument Margin Rate Range, Minimum	4.50%															1.50%		0.50%			1.00%
Debt Instrument Margin Rate Range, Maximum															2.25%		1.25%				1.75%
Line of Credit Facility, Commitment Fee Percentage													0.50%									0.50%	0.375%
Debt Instrument, Covenant Description			4.00 to 1.00	6.00 to 1.00	4.00 to 1.00	4.75 to 1.00	4.50 to 1.00	4.25 to 1.00	5.00 to 1.00
Increase to Applicable Margin, Credit Facility													0.25%
Credit Facility Borrowing Capacity Margin													50.00%
Credit Facility Lender Fee													0.05%
Additional Interest Payment, Credit Facility													2,000,000
Minimum Collateral Value, Credit Facility													75,000,000
Debt Outstanding Principal Amount										75,000,000		50,000,000				50,000,000
Long-term Debt															125,000,000
Line Of Credit Facility Extended Borrowing Capacity																			900,000,000
Debt Instrument Interest Rate In Addition To Eurodollar Rate																			1.00%
Percentage above LIBOR rate																						2.75%	2.00%
Acceleration of Principal Amount Due, Credit Facility																			50,000,000
Long-term Debt, Gross	13,449,000,000	12,620,000,000									50,000,000
Line of Credit Facility, Amount Outstanding													$ 832,000,000						$ 408,000,000	$ 15,000,000				$ 600,000,000