Fair Value Fair Value (Details 4) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Fair Value of Financial Instruments [Line Items]
Notes Receivable Excudling Capital Leases	$ 39	$ 48
Notes Receivable, Fair Value Disclosure		48
Dividends Payable, Current	107	99
Dividends Payable Fair Value Disclosure		99
Short-term Debt	240	419
Notes Payable, Fair Value Disclosure		419
Long-term Debt	7,813	7,682
Long-term Debt, Fair Value		8,757
Fair Value, Inputs, Level 1 [Member]
Fair Value of Financial Instruments [Line Items]
Notes Receivable, Fair Value Disclosure	0
Dividends Payable Fair Value Disclosure	107
Notes Payable, Fair Value Disclosure	0
Long-term Debt, Fair Value	507
Fair Value, Inputs, Level 2 [Member]
Fair Value of Financial Instruments [Line Items]
Notes Receivable, Fair Value Disclosure	0
Dividends Payable Fair Value Disclosure	0
Notes Payable, Fair Value Disclosure	240
Long-term Debt, Fair Value	7,453
Fair Value, Inputs, Level 3 [Member]
Fair Value of Financial Instruments [Line Items]
Notes Receivable, Fair Value Disclosure	39
Dividends Payable Fair Value Disclosure	0
Notes Payable, Fair Value Disclosure	0
Long-term Debt, Fair Value	$ 933