Debt and Credit Arrangements Convertible Securities (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended	1 Months Ended	12 Months Ended			12 Months Ended
	Dec. 31, 2012	Mar. 31, 2012 4.25% Notes	Dec. 31, 2011 4.25% Notes	Dec. 31, 2012 4.25% Notes	Mar. 26, 2012 4.25% Notes	Dec. 31, 2012 4.75% Notes	Dec. 31, 2011 4.75% Notes	Dec. 31, 2010 4.75% Notes
Debt Instrument
Amount redeemed or repurchased for cash					$ 399.6
Accrued interest on debt redeemed or repurchased		0.5
Amount of debt converted in common stock		$ 0.4
Number of shares converted from convertible debt		30,000
4.25% Notes, number of convertible shares eliminated from eligible diluted share count due to retirement				33,000,000
4.75% Notes, terms of conversion feature						convertible at any time if the average price of our common stock for 20 trading days immediately preceding the conversion date is greater than or equal to a specified percentage of the conversion price; this percentage was equal to 115.5% in 2012 and declines 0.5% each year until it reaches 110% at maturity
4.75% Notes, earliest convertible date	Feb. 15, 2023
4.75% Notes, latest convertible date	Mar. 15, 2023
4.75% Notes, conversion price						$ 11.86	$ 12.13	$ 12.42
4.75% Notes, conversion rate per note		82.4612				84.3402	82.4612	80.5153
4.75% Notes, conversion shares						16,900,000	16,500,000	16,100,000
Repurchase of 4.75% Notes for cash, common stock, or combination, earliest date						Mar. 15, 2013
Repurchase of 4.75% Notes for cash, common stock, or combination, latest date						Mar. 15, 2018
Repurchase of 4.75% Notes for cash, common stock, or combination due to change of control events, date						Mar. 15, 2013
Redemption of 4.75% Notes for cash, date						Mar. 15, 2013
Convertible Debt Redemption Price						100.00%
Repurchase of 4.25% Notes for cash, date			Mar. 15, 2012