|
Stockholders' equity (Details) (USD $)
In Millions, unless otherwise specified |
3 Months Ended | |
|---|---|---|
|
Mar. 31, 2013
|
Mar. 31, 2012
|
|
| Stock repurchase program | ||
| Stock repurchases, in shares | 9.1 | 21.0 |
| Stock repurchases, in dollars | $ 771 | $ 1,429 |
| X | ||||||||||
|
- Definition
The value of stock repurchased during the period under a stock repurchase program. No definition available.
|
| X | ||||||||||
|
- Details
|
| X | ||||||||||
|
- Definition
Number of shares that have been repurchased and retired during the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|