Debt - Bank Credit Facilities Narrative (Details) (USD $)	3 Months Ended				6 Months Ended
	Jun. 30, 2013 bank_credit_facility	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2013 bank_credit_facility
Long-Term Debt Instrument [Line Items]
Number of revolving bank credit facilities used	2				2
Debt Instrument Margin Rate Range, Minimum					4.50%
Debt Instrument, Covenant Description	4.00 to 1.00	4.75 to 1.00	5.00 to 1.00	6.00 to 1.00
Long-term Debt, Gross	$ 13,057,000,000		$ 12,620,000,000		$ 13,057,000,000
Minimum
Long-Term Debt Instrument [Line Items]
Debt Outstanding Principal Amount	50,000,000				50,000,000
Corporate Revolving Bank Credit Facility
Long-Term Debt Instrument [Line Items]
Borrowing Capacity	4,000,000,000				4,000,000,000
Interest Rate In Addition To Federal Funds Rate					0.50%
Line of Credit Facility, Commitment Fee Percentage					0.50%
Increase to Applicable Margin, Credit Facility	0.25%				0.25%
Credit Facility Borrowing Capacity Margin					50.00%
Credit Facility Lender Fee					0.05%
Minimum Collateral Value, Credit Facility	75,000,000				75,000,000
Line of Credit Facility, Amount Outstanding	0				0
Corporate Revolving Bank Credit Facility | Maximum
Long-Term Debt Instrument [Line Items]
Debt Instrument, Convertible, Effective Interest Rate					2.25%
Long-term Debt	125,000,000				125,000,000
Corporate Revolving Bank Credit Facility | Minimum
Long-Term Debt Instrument [Line Items]
Debt Instrument Margin Rate Range, Minimum					1.50%
Debt Outstanding Principal Amount	50,000,000				50,000,000
Corporate Revolving Bank Credit Facility | Union Bank N.A. | Maximum
Long-Term Debt Instrument [Line Items]
Debt Instrument, Convertible, Effective Interest Rate					1.25%
Corporate Revolving Bank Credit Facility | Union Bank N.A. | Minimum
Long-Term Debt Instrument [Line Items]
Debt Instrument Margin Rate Range, Minimum					0.50%
Oilfield Services Revolving Bank Credit Facility
Long-Term Debt Instrument [Line Items]
Borrowing Capacity	500,000,000				500,000,000
Interest Rate In Addition To Federal Funds Rate					0.50%
Line Of Credit Facility Extended Borrowing Capacity	900,000,000				900,000,000
Debt Instrument Interest Rate In Addition To Eurodollar Rate	1.00%				1.00%
Acceleration of Principal Amount Due, Credit Facility	50,000,000				50,000,000
Line of Credit Facility, Amount Outstanding	399,000,000				399,000,000
Oilfield Services Revolving Bank Credit Facility | In Excess
Long-Term Debt Instrument [Line Items]
Line of Credit Facility, Amount Outstanding	$ 15,000,000				$ 15,000,000
Oilfield Services Revolving Bank Credit Facility | Bank Of America N.A.
Long-Term Debt Instrument [Line Items]
Debt Instrument Margin Rate Range, Minimum					1.00%
Debt Instrument, Convertible, Effective Interest Rate					1.75%
Oilfield Services Revolving Bank Credit Facility | Bank Of America N.A. | Maximum
Long-Term Debt Instrument [Line Items]
Line of Credit Facility, Commitment Fee Percentage					0.50%
Percentage above LIBOR rate					2.75%
Oilfield Services Revolving Bank Credit Facility | Bank Of America N.A. | Minimum
Long-Term Debt Instrument [Line Items]
Line of Credit Facility, Commitment Fee Percentage					0.375%
Percentage above LIBOR rate					2.00%