Debt (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2011
Debt Instrument [Line Items]
Total debt	$ 1,199	$ 1,198	$ 1,198
Less: short-term debt including current maturities	400	400	0
Long-term debt	799	798	1,198
5.375% Senior Notes, due 2012 [Member]
Debt Instrument [Line Items]
Total debt	400	400	400
Debt (Textual) [Abstract]
Interest rate	5.375%	5.375%	5.375%
Unamortized debt discount on senior notes	0.1
5.9% Senior Notes, due 2017 [Member]
Debt Instrument [Line Items]
Total debt	399	399	399
Debt (Textual) [Abstract]
Interest rate	5.90%	5.90%	5.90%
Unamortized debt discount on senior notes	0.5
6.55% Senior Notes, due 2037 [Member]
Debt Instrument [Line Items]
Total debt	399	399	399
Debt (Textual) [Abstract]
Interest rate	6.55%	6.55%	6.55%
Unamortized debt discount on senior notes	1.3
Notes Payable [Member]
Debt Instrument [Line Items]
Total debt	$ 1	$ 0	$ 0