|
Fair Value Fair Value of Financial Instruments (Details) (USD $)
In Millions, unless otherwise specified |
Mar. 31, 2014
|
Dec. 31, 2013
|
|---|---|---|
|
Reported Value Measurement [Member]
|
||
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ||
| Total debt | $ 37,211 | $ 36,193 |
|
Estimate of Fair Value [Member]
|
||
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ||
| Total debt | $ 37,917 | $ 36,248 |