Long-term Debt (Details) (USD $)	6 Months Ended
	Jun. 30, 2013		Dec. 31, 2012
Debt Instrument
Total long-term debt	$ 2,073,400,000		$ 2,277,400,000
Less: current portion	594,800,000	[1]	216,600,000	[1]
Long-term debt, excluding current portion	1,478,600,000		2,060,800,000
Exercised Call Option, Shares, Acquired, Net Share Settlement	1,500,000
6.25% Senior Unsecured Notes due 2014
Debt Instrument
Effective Interest Rate	6.29%
Book Value	352,000,000		352,800,000
Fair Value	371,000,000	[2]	372,600,000
Stated Interest Rate	6.25%
Unamortized Discount	100,000
Debt Maturity Date	Nov. 15, 2014
10.00% Senior Unsecured Notes due 2017
Debt Instrument
Effective Interest Rate	10.38%
Book Value	592,600,000		591,900,000
Fair Value	630,800,000	[2]	660,800,000
Stated Interest Rate	10.00%
Face Amount	600,000,000
Redemption Date of 10.00% Notes	Jul. 15, 2013
Early Redemption Debt Premium of 10.00% Notes	105.00%
Unamortized Discount	7,400,000
Debt Maturity Date	Jul. 15, 2017
2.25% Senior Notes due 2017
Debt Instrument
Effective Interest Rate	2.30%
Book Value	299,400,000		299,300,000
Fair Value	293,500,000		297,800,000
Stated Interest Rate	2.25%
Unamortized Discount	600,000
Debt Maturity Date	Nov. 15, 2017
4.00% Senior Notes due 2022
Debt Instrument
Effective Interest Rate	4.13%
Book Value	247,300,000		247,100,000
Fair Value	241,000,000	[2]	258,700,000
Stated Interest Rate	4.00%
Unamortized Discount	2,700,000
Debt Maturity Date	Mar. 15, 2022
3.75% Senior Notes due 2023
Debt Instrument
Effective Interest Rate	4.32%
Book Value	498,600,000		498,500,000
Fair Value	464,200,000		499,700,000
Stated Interest Rate	3.75%
Unamortized Discount	1,400,000
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
Extinguishment of Debt, Amount	200,000,000
4.75% Notes, Amount Retired for Cash	199,997,000
Conversion Rate	84.3402
Other notes payable and capitalized leases
Debt Instrument
Book Value	83,500,000		87,300,000
Fair Value	$ 81,600,000	[2]	$ 90,800,000	[2]
Common Stock
Debt Instrument
Conversion of convertible notes to common stock, shares	16,900,000

[1] In June 2013, we exercised our option to redeem all of the 10.00% Senior Unsecured Notes due 2017 (the "10.00% Notes") on July 15, 2013, as such, we included our 10.00% Notes in the current portion of long-term debt on our June 30, 2013 unaudited Consolidated Balance Sheet. 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 an option to require us to repurchase their Notes 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.