Financing Arrangements (Details) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended	9 Months Ended		9 Months Ended	1 Months Ended	9 Months Ended			9 Months Ended
	Sep. 30, 2011 3.375% Senior Notes due September 15, 2021	Sep. 30, 2013 3.375% Senior Notes due September 15, 2021	Dec. 31, 2012 3.375% Senior Notes due September 15, 2021	Sep. 30, 2013 3.375% Senior Notes due September 15, 2021 Change of control triggering event	Feb. 29, 2004 1.5% Convertible Senior Notes due February 15, 2024	Sep. 30, 2013 1.5% Convertible Senior Notes due February 15, 2024	Sep. 30, 2012 1.5% Convertible Senior Notes due February 15, 2024	Dec. 31, 2012 1.5% Convertible Senior Notes due February 15, 2024	Sep. 30, 2013 1.5% Convertible Senior Notes due February 15, 2024 Maximum
Financing Arrangements
Issue price of notes	$ 500				$ 330
Debt instrument interest rate (as a percent)	3.375%	3.375%	3.375%		1.50%	1.50%		1.50%
Proceeds from notes	492				323
Redemption option, price as a percentage of principal		100.00%		101.00%
Debt conversion, amount of original debt							$ 0.9		$ 0.1
Debt conversions (in shares)						1,562	17,352