Debt (Fair Value of Debt) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012		Dec. 31, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 10,591		$ 10,425
Long Term Debt, Fair Value Excluding Capital Leases	10,722		10,371
Debt Excluding Capital Leases	10,210		10,014
Corporate Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	6,340		6,219
Long-term Debt	5,892		5,892
Notes Payable and Other Payables excluding Leases [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	1,667	[1]	1,467	[1]
Long-term Debt	1,705	[1]	1,504	[1]
Loans Payable [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	1,630		1,615
Long-term Debt	1,638		1,646
Secured Debt [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	1,085		1,070
Long-term Debt	$ 975		$ 972

[1] Excludes a lease that is accounted for as a failed sale-leaseback transaction under U.S. GAAP