Debt (Fair Value of Debt) (Details) (USD $)
In Millions, unless otherwise specified

Sep. 30, 2013

Dec. 31, 2012

Portion at Fair Value, Fair Value Disclosure [Member]

Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]

Notes Payable, Fair Value Disclosure

$ 5,652

$ 5,863

Subsidiaries Notes Disclosure

0

1,075

Notes Payable, Other Payables, Disclosure

1,738

^[1]

1,599

^[1]

Subsidiaries Term Loan

1,171

0

Loans Payable, Fair Value Disclosure

2,446

2,489

Debt Excluding Capital Leases

11,007

11,026

Carrying (Reported) Amount, Fair Value Disclosure [Member]

Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]

Notes Payable, Fair Value Disclosure

5,304

5,303

Subsidiaries Notes Disclosure

0

978

Notes Payable, Other Payables, Disclosure

1,735

^[1]

1,629

^[1]

Subsidiaries Term Loan

1,194

0

Loans Payable, Fair Value Disclosure

2,444

2,463

Debt Excluding Capital Leases

$ 10,677

$ 10,373

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