|
Income taxes (Details 2) (USD $)
In Millions, unless otherwise specified |
12 Months Ended | ||
|---|---|---|---|
|
Dec. 31, 2012
|
Dec. 31, 2011
|
Dec. 31, 2010
|
|
| Reconciliation of total gross amounts of unrecognized tax benefits (excluding interest, penalties, foreign tax credits and the federal tax benefit of state taxes related to unrecognized tax benefits) | |||
| Balance at beginning of year | $ 975 | $ 920 | $ 1,140 |
| Additions based on tax positions related to the current year | 300 | 283 | 305 |
| Reductions for tax positions of prior years | (45) | (7) | (110) |
| Settlements | (30) | (221) | (415) |
| Balance at end of year | $ 1,200 | $ 975 | $ 920 |
| X | ||||||||||
|
- Details
|
| X | ||||||||||
|
- Definition
The gross amount of unrecognized tax benefits pertaining to uncertain tax positions taken in tax returns as of the balance sheet date. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
|
- Definition
The gross amount of decreases in unrecognized tax benefits resulting from tax positions taken in prior period tax returns, excluding amounts pertaining to examined tax returns. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
|
- Definition
The gross amount of decreases in unrecognized tax benefits resulting from settlements with taxing authorities. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
|
- Definition
The gross amount of increases in unrecognized tax benefits resulting from tax positions that have been or will be taken in the tax return for the current period, excluding amounts pertaining to examined tax returns. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|