Debt (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Debt Type Details [Abstract]
Commercial Paper	$ 225	$ 100
Long Term Debt Current	2	4
Total short-term debt	227	104
Statement Line Items [Line Items]
Long-term debt	4,990	4,990
Other Long Term Debt [Member]
Statement Line Items [Line Items]
Long-term debt	43	43
Notes Due 2016275 Interest [Member]
Statement Line Items [Line Items]
Long-term debt	600	600
Interest rate of long term debt issued	2.75%
Notes Due 20175375 Interest [Member]
Statement Line Items [Line Items]
Long-term debt	250	250
Interest rate of long term debt issued	5.375%
Notes Due 2018635 Interest [Member]
Statement Line Items [Line Items]
Long-term debt	131	131
Interest rate of long term debt issued	6.35%
Notes Due 201985 Interest [Member]
Statement Line Items [Line Items]
Long-term debt	251	251
Interest rate of long term debt issued	8.50%
Notes Due 20204375 Interest [Member]
Statement Line Items [Line Items]
Long-term debt	249	249
Interest rate of long term debt issued	4.375%
Notes Due 20205125 Interest [Member]
Statement Line Items [Line Items]
Long-term debt	299	299
Interest rate of long term debt issued	5.125%
Notes Due 202145 Interest [Member]
Statement Line Items [Line Items]
Long-term debt	298	298
Interest rate of long term debt issued	4.50%
Notes Due 2021637 Interest [Member]
Statement Line Items [Line Items]
Long-term debt	78	78
Interest rate of long term debt issued	6.37%
Notes Due 20224 Interest [Member]
Statement Line Items [Line Items]
Long-term debt	743	743
Interest rate of long term debt issued	4.00%
Notes Due 2023765 Interest [Member]
Statement Line Items [Line Items]
Long-term debt	100	100
Interest rate of long term debt issued	7.65%
Notes Due 202383 Interest [Member]
Statement Line Items [Line Items]
Long-term debt	17	17
Interest rate of long term debt issued	8.30%
Debentures Due 20277875 Interest [Member]
Statement Line Items [Line Items]
Long-term debt	300	300
Interest rate of long term debt issued	7.875%
Step Down Notes Due 203383 Interest [Member]
Statement Line Items [Line Items]
Long-term debt	83	83
Interest rate of long term debt issued	8.30%
Notes Due 2036615 Interest [Member]
Statement Line Items [Line Items]
Long-term debt	500	500
Interest rate of long term debt issued	6.15%
Notes Due 20415875 Interest [Member]
Statement Line Items [Line Items]
Long-term debt	298	298
Interest rate of long term debt issued	5.875%
Notes Due 20425375 Interest [Member]
Statement Line Items [Line Items]
Long-term debt	$ 750	$ 750
Interest rate of long term debt issued	5.375%