Long-term Debt (Details) (USD $)	3 Months Ended
	Mar. 31, 2013		Dec. 31, 2012
Debt Instrument
Total long-term debt	$ 2,073,500,000		$ 2,277,400,000
Less: current portion	1,900,000	[1]	216,600,000	[1]
Long-term debt, excluding current portion	2,071,600,000		2,060,800,000
Exercised Call Option, Shares, Acquired, Net Share Settlement	0.8
6.25% Senior Unsecured Notes due 2014
Debt Instrument
Effective Interest Rate	6.29%
Book Value	352,400,000		352,800,000
Fair Value	376,800,000	[2]	372,600,000
Stated Interest Rate	6.25%
Debt Instrument, Unamortized Discount	200,000
Debt Maturity Date	Nov. 15, 2014
10.00% Senior Unsecured Notes due 2017
Debt Instrument
Effective Interest Rate	10.38%
Book Value	592,300,000		591,900,000
Fair Value	642,800,000	[2]	660,800,000
Stated Interest Rate	10.00%
Debt Instrument, Unamortized Discount	7,700,000
Debt Maturity Date	Jul. 15, 2017
2.25% Senior Notes due 2017
Debt Instrument
Effective Interest Rate	2.30%
Book Value	299,300,000		299,300,000
Fair Value	299,000,000		297,800,000
Stated Interest Rate	2.25%
Debt Instrument, Unamortized Discount	700,000
Debt Maturity Date	Nov. 15, 2017
4.00% Senior Notes due 2022
Debt Instrument
Effective Interest Rate	4.13%
Book Value	247,200,000		247,100,000
Fair Value	252,400,000	[2]	258,700,000
Stated Interest Rate	4.00%
Debt Instrument, Unamortized Discount	2,800,000
Debt Maturity Date	Mar. 15, 2022
3.75% Senior Notes due 2023
Debt Instrument
Effective Interest Rate	4.32%
Book Value	498,500,000		498,500,000
Fair Value	482,900,000		499,700,000
Stated Interest Rate	3.75%
Debt Instrument, Unamortized Discount	1,500,000
Debt Maturity Date	Feb. 15, 2013
4.75% Notes
Debt Instrument
Book Value	0		200,500,000
Fair Value	0	[2]	202,800,000
Stated Interest Rate	4.75%
Debt Maturity Date	Mar. 15, 2023
4.75% Notes, Amount Retired	200,000,000
4.75% Notes, Amount Retired for Cash	199,997,000
Current conversion ratio	84.3402
Other notes payable and capitalized leases
Debt Instrument
Book Value	83,800,000		87,300,000
Fair Value	$ 83,900,000	[2]	$ 90,800,000	[2]
Common Stock
Debt Instrument
Conversion of convertible notes to common stock, shares	16,900,000

[1] We included our 4.75% Convertible Senior Notes due 2023 (the “4.75% Notes”) in the current portion of long-term debt on our December 31, 2012 Consolidated Balance Sheet because holders of the 4.75% Notes had a repurchase option for cash, stock or a combination, at our election, at par on March 15, 2013. The 4.75% Notes were retired in the first quarter of 2013.

[2] See Note 11 for information on the fair value measurement of our long-term debt.