Debt (Details) (USD $)	12 Months Ended																							12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Apr. 23, 2013 Revolving Credit Facility	Dec. 31, 2013 Senior notes due August 2023	Dec. 31, 2012 Senior notes due August 2023	Dec. 31, 2013 Senior notes due September 2019	Dec. 31, 2012 Senior notes due September 2019	Dec. 31, 2013 Senior notes due September 2039	Dec. 31, 2012 Senior notes due September 2039	Dec. 31, 2013 Senior notes due August 2043	Dec. 31, 2012 Senior notes due August 2043	Dec. 31, 2013 Senior notes due September 2038	Dec. 31, 2012 Senior notes due September 2038	Dec. 31, 2013 Senior notes due August 2016	Dec. 31, 2012 Senior notes due August 2016	Dec. 31, 2013 Senior notes due November 2021	Dec. 31, 2012 Senior notes due November 2021	Dec. 31, 2013 Senior notes due November 2041	Dec. 31, 2012 Senior notes due November 2041	Dec. 31, 2013 Senior notes due August 2018	Dec. 31, 2012 Senior notes due August 2018	Dec. 31, 2013 Senior notes due September 2018	Dec. 31, 2012 Senior notes due September 2018	Dec. 31, 2013 Senior debentures due August 2096	Dec. 31, 2012 Senior debentures due August 2096	Dec. 31, 2013 Senior debentures due February 2021	Dec. 31, 2012 Senior debentures due February 2021	Dec. 31, 2013 Other Debt Obligations [Member]	Dec. 31, 2012 Other Debt Obligations [Member]
Debt Instrument [Line Items]
Long-term Debt, Percentage Bearing Fixed Interest, Amount	$ 7,800,000,000	$ 4,820,000,000
Long-term debt	7,816,000,000	4,820,000,000		1,098,000,000	0	997,000,000	997,000,000	995,000,000	995,000,000	898,000,000	0	800,000,000	800,000,000	600,000,000	0	498,000,000	498,000,000	498,000,000	498,000,000	400,000,000	0	400,000,000	400,000,000	293,000,000	293,000,000	184,000,000	184,000,000	155,000,000	155,000,000
Maturity date				August 2023			September 2019		September 2039	August 2043			September 2038	August 2016			November 2021		November 2041	August 2018			September 2018		August 2096		February 2021
Interest rate (in hundredths)				3.50%			6.15%		7.45%	4.75%			6.70%	1.00%			3.25%		4.50%	2.00%			5.90%	7.60%	7.60%	8.75%	8.75%
Debt instrument call feature description	We may redeem all of our senior notes from time to time or all of the notes of each series at any time at the applicable redemption prices, plus accrued and unpaid interest.
Debt instruments non-call feature description																								may not be redeemed prior to maturity
Line of credit facility, maximum borrowing capacity			3,000,000,000
Line of Credit Facility, Expiration Date	Apr. 23, 2018
Long-term Debt, Maturities, Repayments of Principal in Year Three	600,000,000
Long-term Debt, Maturities, Repayments of Principal in Year Four	45,000,000
Long-term debt due in 2017	800,000,000
Line of Credit Facility, Remaining Borrowing Capacity	$ 3,000,000,000