Postretirement Benefits (Details 4) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Fair value measurements of pension plan assets
Total	$ 348	$ 0
Employee pension plan
Fair value measurements of pension plan assets
Total	348	328	279	218
Employee pension plan | Total
Fair value measurements of pension plan assets
Total	348	328
Employee pension plan | Level 1
Fair value measurements of pension plan assets
Total	2	3
Employee pension plan | Level 2
Fair value measurements of pension plan assets
Total	346	325
Employee pension plan | Level 3
Fair value measurements of pension plan assets
Total	0	0
Employee pension plan | US equity index | Total
Fair value measurements of pension plan assets
Total	58	55
Employee pension plan | US equity index | Level 1
Fair value measurements of pension plan assets
Total	0	0
Employee pension plan | US equity index | Level 2
Fair value measurements of pension plan assets
Total	58	55
Employee pension plan | US equity index | Level 3
Fair value measurements of pension plan assets
Total	0	0
Employee pension plan | US large capitalization core equity | Total
Fair value measurements of pension plan assets
Total	54	51
Employee pension plan | US large capitalization core equity | Level 1
Fair value measurements of pension plan assets
Total	0	0
Employee pension plan | US large capitalization core equity | Level 2
Fair value measurements of pension plan assets
Total	54	51
Employee pension plan | US large capitalization core equity | Level 3
Fair value measurements of pension plan assets
Total	0	0
Employee pension plan | International risk-controlled equity | Total
Fair value measurements of pension plan assets
Total	53	50
Employee pension plan | International risk-controlled equity | Level 1
Fair value measurements of pension plan assets
Total	0	0
Employee pension plan | International risk-controlled equity | Level 2
Fair value measurements of pension plan assets
Total	53	50
Employee pension plan | International risk-controlled equity | Level 3
Fair value measurements of pension plan assets
Total	0	0
Employee pension plan | US small capitalization core equity | Total
Fair value measurements of pension plan assets
Total	28	26
Employee pension plan | US small capitalization core equity | Level 1
Fair value measurements of pension plan assets
Total	0	0
Employee pension plan | US small capitalization core equity | Level 2
Fair value measurements of pension plan assets
Total	28	26
Employee pension plan | US small capitalization core equity | Level 3
Fair value measurements of pension plan assets
Total	0	0
Employee pension plan | International small capitalization risk-controlled equity | Total
Fair value measurements of pension plan assets
Total	8	8
Employee pension plan | International small capitalization risk-controlled equity | Level 1
Fair value measurements of pension plan assets
Total	0	0
Employee pension plan | International small capitalization risk-controlled equity | Level 2
Fair value measurements of pension plan assets
Total	8	8
Employee pension plan | International small capitalization risk-controlled equity | Level 3
Fair value measurements of pension plan assets
Total	0	0
Employee pension plan | Emerging markets equity | Total
Fair value measurements of pension plan assets
Total	7	7
Employee pension plan | Emerging markets equity | Level 1
Fair value measurements of pension plan assets
Total	0	0
Employee pension plan | Emerging markets equity | Level 2
Fair value measurements of pension plan assets
Total	7	7
Employee pension plan | Emerging markets equity | Level 3
Fair value measurements of pension plan assets
Total	0	0
Employee pension plan | Long duration fixed income | Total
Fair value measurements of pension plan assets
Total	55	51
Employee pension plan | Long duration fixed income | Level 1
Fair value measurements of pension plan assets
Total	0	0
Employee pension plan | Long duration fixed income | Level 2
Fair value measurements of pension plan assets
Total	55	51
Employee pension plan | Long duration fixed income | Level 3
Fair value measurements of pension plan assets
Total	0	0
Employee pension plan | Broad market fixed income | Total
Fair value measurements of pension plan assets
Total	53	49
Employee pension plan | Broad market fixed income | Level 1
Fair value measurements of pension plan assets
Total	0	0
Employee pension plan | Broad market fixed income | Level 2
Fair value measurements of pension plan assets
Total	53	49
Employee pension plan | Broad market fixed income | Level 3
Fair value measurements of pension plan assets
Total	0	0
Employee pension plan | Long duration corporate fixed income | Total
Fair value measurements of pension plan assets
Total	30	28
Employee pension plan | Long duration corporate fixed income | Level 1
Fair value measurements of pension plan assets
Total	0	0
Employee pension plan | Long duration corporate fixed income | Level 2
Fair value measurements of pension plan assets
Total	30	28
Employee pension plan | Long duration corporate fixed income | Level 3
Fair value measurements of pension plan assets
Total	0	0
Employee pension plan | Institutional money market fund | Total
Fair value measurements of pension plan assets
Total	2	3
Employee pension plan | Institutional money market fund | Level 1
Fair value measurements of pension plan assets
Total	2	3
Employee pension plan | Institutional money market fund | Level 2
Fair value measurements of pension plan assets
Total	0	0
Employee pension plan | Institutional money market fund | Level 3
Fair value measurements of pension plan assets
Total	$ 0	$ 0