Postretirement Benefit Plans (Details 12) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets	$ 192	$ 195
Pension [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets	184	187	176
Pension [Member] \| Domestic [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets	60	47
Pension [Member] \| International [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets	33	15
Pension [Member] \| Emerging Markets [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets	16	19
Pension [Member] \| Fixed income [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets	63
Pension [Member] \| Cash and other [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets	12
Pension [Member] \| Private equity [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets		55
Pension [Member] \| Absolute return (hedge funds) [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets		32
Pension [Member] \| Commodities, fixed income and other [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets		19
Pension [Member] \| Level 1 [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets		54
Pension [Member] \| Level 1 [Member] \| Domestic [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets		36
Pension [Member] \| Level 1 [Member] \| International [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets		10
Pension [Member] \| Level 1 [Member] \| Emerging Markets [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets		8
Pension [Member] \| Level 1 [Member] \| Private equity [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets		0
Pension [Member] \| Level 1 [Member] \| Absolute return (hedge funds) [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets		0
Pension [Member] \| Level 1 [Member] \| Commodities, fixed income and other [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets		0
Pension [Member] \| Level 2 [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets	184	51
Pension [Member] \| Level 2 [Member] \| Domestic [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets	60	7
Pension [Member] \| Level 2 [Member] \| International [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets	33	0
Pension [Member] \| Level 2 [Member] \| Emerging Markets [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets	16	9
Pension [Member] \| Level 2 [Member] \| Fixed income [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets	63
Pension [Member] \| Level 2 [Member] \| Cash and other [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets	12
Pension [Member] \| Level 2 [Member] \| Private equity [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets		7
Pension [Member] \| Level 2 [Member] \| Absolute return (hedge funds) [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets		12
Pension [Member] \| Level 2 [Member] \| Commodities, fixed income and other [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets		16
Pension [Member] \| Level 3 [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets	0	82	79
Pension [Member] \| Level 3 [Member] \| Equities [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets	0	11	9
Pension [Member] \| Level 3 [Member] \| Domestic [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets		4
Pension [Member] \| Level 3 [Member] \| International [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets		5
Pension [Member] \| Level 3 [Member] \| Emerging Markets [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets		2
Pension [Member] \| Level 3 [Member] \| Private equity [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets	0	48	47
Pension [Member] \| Level 3 [Member] \| Absolute return (hedge funds) [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets	0	20	21
Pension [Member] \| Level 3 [Member] \| Commodities, fixed income and other [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets	0	3	2
Other Benefits [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets	8	8	8
Other Benefits [Member] \| Domestic [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets	0	0
Other Benefits [Member] \| International [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets	0	0
Other Benefits [Member] \| Emerging Markets [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets	0	0
Other Benefits [Member] \| Fixed income [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets	0
Other Benefits [Member] \| Cash and other [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets	8
Other Benefits [Member] \| Private equity [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets		0
Other Benefits [Member] \| Absolute return (hedge funds) [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets		0
Other Benefits [Member] \| Commodities, fixed income and other [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets		8
Other Benefits [Member] \| Level 3 [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets	8	8
Other Benefits [Member] \| Level 3 [Member] \| Domestic [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets	0	0
Other Benefits [Member] \| Level 3 [Member] \| International [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets	0	0
Other Benefits [Member] \| Level 3 [Member] \| Emerging Markets [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets	0	0
Other Benefits [Member] \| Level 3 [Member] \| Fixed income [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets	0
Other Benefits [Member] \| Level 3 [Member] \| Cash and other [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets	8
Other Benefits [Member] \| Level 3 [Member] \| Private equity [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets		0
Other Benefits [Member] \| Level 3 [Member] \| Absolute return (hedge funds) [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets		0
Other Benefits [Member] \| Level 3 [Member] \| Commodities, fixed income and other [Member]
Fair value of plan assets held by our postretirement benefit plans
Fair value of plan assets		$ 8

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.

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