Debt (Details) (4.50% convertible senior notes due 2013 [Member], USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012
4.50% convertible senior notes due 2013 [Member]
Debt (Textual) [Abstract]
Principal amount of convertible notes outstanding	$ 215
Conversion threshold price per share	$ 17.06
Conversion terms: Minimum trading days of common stock within 30 consecutive trading days of preceding calendar quarter	20 days
Conversion terms: Consecutive trading days ending on last trading day of preceding calendar quarter	30 days
Convertible at holder's option, convertible date description	through June 30, 2012
Stock Price on March 31, 2012	$ 27.83
Amount if converted value in excess of face amount	241
Potential incremental share settlement in excess of the face amount of the notes that could be issued upon conversion of convertible notes, after giving effect to the exercise of the call options and warrants	7
Potential incremental cash payment in excess of the face amount of the notes upon conversion of convertible notes, after giving effect to the exercise of the call options and warrants	$ 198