Debt (Narrative) (Details)	3 Months Ended			12 Months Ended			3 Months Ended					12 Months Ended	3 Months Ended		12 Months Ended		12 Months Ended
	Jun. 30, 2011 USD ($)	Jun. 30, 2011 CNY	Sep. 30, 2010 USD ($)	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)	Dec. 31, 2009 USD ($)	Dec. 31, 2010 Notes 6.05% [Member] USD ($)	Sep. 30, 2010 Notes 5.75% [Member] USD ($)	Sep. 30, 2010 Notes 4.25% [Member] USD ($)	Sep. 30, 2010 Notes 6.2% [Member] USD ($)	Sep. 30, 2010 Notes 5.9% [Member] USD ($)	Dec. 31, 2010 Notes 6.25% [Member] USD ($)	Jun. 30, 2009 Notes 6.625% [Member] USD ($)	Jun. 30, 2009 Notes 7% [Member] USD ($)	Dec. 31, 2009 Notes 6.3% [Member] USD ($)	Dec. 31, 2010 Amended Credit Facility [Member] USD ($)	Dec. 31, 2011 Debentures, 6.75%, Due 2013 [Member]	Dec. 31, 2011 Debentures, 8.875%, Due 2016 [Member]	Dec. 31, 2011 Debentures, 8.875%, Due 2021 [Member]	Dec. 31, 2011 Medium-Term Notes, Average Rate 7.66%, Due Through 2023 [Member]	Dec. 31, 2011 Debentures, 6.85%, Due 2029 [Member]	Dec. 31, 2011 Debentures, Callable, 7.25%, Due 2036 [Member]	Dec. 31, 2011 Other, Average Rate 5.25%, Due Through 2037 [Member]
Debt Instrument [Line Items]
Weighted average interest rate				2.10%	4.90%
Fair value of long-term debt				$ 2,600,000,000	$ 2,400,000,000
Line of credit facility, maximum borrowing amount	635,000,000	4,000,000,000														1,000,000,000
Line of credit facility number of installments	6	6
Line of credit facility final payment due, years from date of first advance	5	5
Interest costs capitalized as part of property				46,000,000	20,000,000	29,000,000
Credit facility approximately borrowed				120,000,000
Line of credit facility, expiration date					December 2015
Repurchase of debt					364,000,000		100,000,000
Redemption of principal												48,000,000			54,000,000
Par value of issued senior unsecured notes								400,000,000	300,000,000				250,000,000	100,000,000
Interest rate on debt							6.05%	5.75%	4.25%	6.20%	5.90%	6.25%	6.625%	7.00%	6.30%		6.75%	8.875%	8.875%	7.66%	6.85%	7.25%	5.25%
Maturity date							Jun. 15, 2015	Aug. 15, 2040	Aug. 15, 2020	Mar. 15, 2016	Mar. 15, 2014	Feb. 18, 2010	May 15, 2019	May 15, 2024	Mar. 01, 2009
Debt maturity date																	2013	2016	2021	2023	2029	2036	2037
Proceeds from issuance of long-term debt and capital securities, net								394,000,000	295,000,000				248,000,000	98,000,000
Net carrying amount of senior unsecured note debt			234,000,000				100,000,000
Repurchase of senior unsecured notes										126,000,000	100,000,000
Net loss on early redemption of senior unsecured notes			30,000,000		30,000,000
Capital lease obligations				$ 182,000,000	$ 172,000,000