Debt And Interest Expense (Convertible Debentures) (Narrative) (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	1 Months Ended	12 Months Ended
	Aug. 31, 2007 Rate	Dec. 31, 2012 Rate	Dec. 31, 2011	Dec. 31, 2010	Aug. 15, 2007 Rate
Debt Disclosure [Abstract]
Principal amount of convertible debentures		$ 1,250,000,000	$ 1,250,000,000		$ 1,250,000,000
Convertible debenture, interest rate	3.25%				3.25%
Convertible debenture, maturity date	Aug. 15, 2037
Conversion rate per 1000 principal amount	29.0968
Denominator of principal value upon which conversion is based	1,000
Conversion price					$ 34.37
Common stock reserved for issuance upon the conversion of convertible debt		36.4
Earlier conversion date	Aug. 15, 2017
Minimum required sales price as a percentage of conversion price	150.00%
Conversion threshold minimum stock price as a percentage of conversion price	130.00%
Percentage of maximum required trading price per convertible debentures	98.00%
Latest conversion date	May 15, 2037
Additional common shares potentially issuable based on if-converted value of convertible debentures		4.2
Purchase price as percentage of principal amount of convertible debt	100.00%
Net proceeds from issuance of convertible debenture	1,224,223,000
Debt issuance costs	25,777,000
Discount rate	8.50%	8.50%
Debt Instrument, Convertible, Remaining Discount Amortization Period		24 years 227 days
Effective interest rate	8.39%
Contingent interest on convertible debentures			$ 100,000,000	$ 109,100,000