Postemployment benefit plans (Details 3) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
U.S. Pension Benefits
Change in plan assets:
Fair value of plan assets, beginning of year	$ 9,997	$ 10,760	$ 9,029
Actual return on plan assets	1,235	(270)	1,628
Foreign currency exchange rates	0	0	0
Company contributions	580	212	919
Participant contributions	0	0	0
Benefits paid	(831)	(823)	(820)
Settlements and special termination benefits	0	0	0
Acquisitions / other	0	118	4
Fair value of plan assets, end of year	10,981	9,997	10,760
Information about plan asset allocations
Rebalancing of plan assets outside of target allocation (as a percent)	5.00%
U.S. Pension Benefits \| Equities
Information about plan asset allocations
Target allocation of plan assets (as a percent)	70.00%
Portion of equity securities invested in U.S. equities (as a percent)	65.00%
U.S. Pension Benefits \| Debt securities
Information about plan asset allocations
Target allocation of plan assets (as a percent)	30.00%
U.S. Pension Benefits \| Real estate
Change in plan assets:
Fair value of plan assets, end of year	8	8	10
Non-U.S. Pension Benefits
Change in plan assets:
Fair value of plan assets, beginning of year	2,818	2,880	2,797
Actual return on plan assets	368	(83)	193
Foreign currency exchange rates	47	(1)	17
Company contributions	446	234	58
Participant contributions	9	9	9
Benefits paid	(190)	(187)	(168)
Settlements and special termination benefits	(72)	(41)	(51)
Acquisitions / other	0	7	25
Fair value of plan assets, end of year	3,426	2,818	2,880
Non-U.S. Pension Benefits \| Equities
Information about plan asset allocations
Target allocation of plan assets (as a percent)	58.00%
Non-U.S. Pension Benefits \| Debt securities
Information about plan asset allocations
Target allocation of plan assets (as a percent)	31.00%
Non-U.S. Pension Benefits \| Real estate
Change in plan assets:
Fair value of plan assets, beginning of year	197
Fair value of plan assets, end of year	218		179
Information about plan asset allocations
Target allocation of plan assets (as a percent)	7.00%
Non-U.S. Pension Benefits \| Other
Information about plan asset allocations
Target allocation of plan assets (as a percent)	4.00%
Other Postretirement Benefits
Change in plan assets:
Fair value of plan assets, beginning of year	814	996	1,063
Actual return on plan assets	117	(45)	129
Foreign currency exchange rates	0	0	0
Company contributions	204	207	138
Participant contributions	48	44	45
Benefits paid	(394)	(388)	(379)
Settlements and special termination benefits	0	0	0
Acquisitions / other	0	0	0
Fair value of plan assets, end of year	$ 789	$ 814	$ 996
Other Postretirement Benefits \| Equities
Information about plan asset allocations
Target allocation of plan assets (as a percent)	80.00%
Portion of equity securities invested in U.S. equities (as a percent)	67.00%
Other Postretirement Benefits \| Debt securities
Information about plan asset allocations
Target allocation of plan assets (as a percent)	20.00%

The amount of change in plan assets due to settlements and special termination benefits.

No definition available.

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- Definition

This element represents the range of rebalancing of plan assets outside of the target allocation.

+ References

No definition available.

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- Definition

This element represents the portion of equity securities invested in U.S. large cap, small cap and private companies for the plan assets of U.S. pension and other postretirement benefit plans.

+ References

No definition available.

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- Definition

The difference between fair value of plan assets at the end of the period and the fair value at the beginning of the period, adjusted for contributions and payments of benefits during the period, and after adjusting for taxes and other expenses, as applicable.

+ References

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- Definition

The amount of payments made for which participants are entitled under a pension plan, including pension benefits, death benefits, and benefits due on termination of employment. Also includes payments made under a postretirement benefit plan, including prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services. This item represents a periodic decrease to the plan obligations and a decrease to plan assets.

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- Definition

The amount of increase in the plan assets attributed to a business combination.

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- Definition

The increase in the fair value of plan assets from contributions made by the employer.

+ References

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- Definition

The amount of contributions made by plan participants. This item represents a periodic increase to the plan obligation and an increase to plan assets.

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- Definition

Assets, usually stocks, bonds, and other investments, that have been segregated and restricted (usually in a trust) to provide benefits, at their fair value as of the measurement date. Plan assets include amounts contributed by the employer (and by employees for a contributory plan) and amounts earned from investing the contributions, less benefits paid. If a plan has liabilities other than for benefits, those non-benefit obligations may be considered as reductions of plan assets.

+ References

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- Definition

The amount of increase or decrease in plan assets attributed to foreign currency changes. The effects of foreign currency exchange rate changes that are to be disclosed are those applicable to plans of a foreign operation whose functional currency is not the reporting currency.

+ References

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- Definition

Target allocation of investments of this type to total plan assets presented on a weighted average basis.

+ References

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