Fair Value of Financial Instruments #2 (Details) (USD $)	3 Months Ended	6 Months Ended				1 Months Ended			1 Months Ended		1 Months Ended		1 Months Ended
	Jun. 30, 2013	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012	May 31, 2013 Senior Notes	May 31, 2013 Senior Notes August 2014 Maturity	May 31, 2013 Senior Notes November 2015 Maturity	May 31, 2013 Senior Notes 5-Year Term	May 31, 2013 Senior Notes 5-Year Term June 2018 Maturity [Member]	May 31, 2013 Senior Notes 10-Year Term	May 31, 2013 Senior Notes 10-Year Term August 2023 Maturity [Member]	May 31, 2013 Senior Notes 30-Year Term	May 31, 2013 Senior Notes 30-Year Term June 2043 Maturity [Member]	Jun. 30, 2013 Cash Flow Hedging	Dec. 31, 2012 Cash Flow Hedging
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Transfers of financial instruments, Level 1, assets, net		$ 0
Transfers of financial instruments, Level 1, liabilities, net		0
Transfers of financial instruments, Level 2, assets, net		0
Transfers of financial instruments, Level 2, liabilities, net		0
Transfers of financial instruments, Level 3, assets, net		0
Transfers of financial instruments, Level 3, liabilities, net		0
Investments in Marketable Securities [Abstract]
Marketable Securities, Noncurrent	274,000,000	274,000,000		261,000,000
Derivative Financial Instruments and Hedging Activities [Abstract]
Derivative, Notional Amount	169,000,000	169,000,000		164,000,000										68,000,000	110,000,000
Long-term Debt [Abstract]
Debt instrument, face amount					2,850,000,000				850,000,000		1,050,000,000		950,000,000
Debt Instrument, Maturity Date						Aug. 01, 2014	Nov. 15, 2015		Jun. 01, 2018		Aug. 01, 2023		Jun. 01, 2043
Debt instrument, stated interest rate (percent)						3.70%	1.85%	1.75%		3.25%		4.75%
Repayments of long-term debt		877,000,000	0			350,000,000	500,000,000
Redemption Premium	$ 30,000,000