Long-term Debt (Details) (USD $)	3 Months Ended			9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012	Sep. 30, 2013		Sep. 30, 2012	Dec. 31, 2012
Debt Instrument
Total long-term debt	$ 1,483,200,000			$ 1,483,200,000			$ 2,277,400,000
Less: current portion	2,200,000	[1]		2,200,000	[1]		216,600,000	[1]
Long-term debt, excluding current portion	1,481,000,000			1,481,000,000			2,060,800,000
Loss on early extinguishment of debt	45,200,000		0	45,200,000		0
Exercised Call Option, Shares, Acquired, Net Share Settlement	1,500,000			1,500,000
6.25% Senior Unsecured Notes due 2014
Debt Instrument
Effective Interest Rate	6.29%			6.29%
Book Value	351,600,000			351,600,000			352,800,000
Fair Value	369,400,000	[2]		369,400,000	[2]		372,600,000	[2]
Stated Interest Rate	6.25%			6.25%
Debt Instrument, Unamortized Discount	100,000			100,000
Debt Maturity Date				Nov. 15, 2014
2.25% Senior Notes due 2017
Debt Instrument
Effective Interest Rate	2.30%			2.30%
Book Value	299,400,000			299,400,000			299,300,000
Fair Value	296,700,000	[2]		296,700,000	[2]		297,800,000	[2]
Stated Interest Rate	2.25%			2.25%
Debt Instrument, Unamortized Discount	600,000			600,000
Debt Maturity Date				Nov. 15, 2017
4.00% Senior Notes due 2022
Debt Instrument
Effective Interest Rate	4.13%			4.13%
Book Value	247,300,000			247,300,000			247,100,000
Fair Value	242,000,000	[2]		242,000,000	[2]		258,700,000	[2]
Stated Interest Rate	4.00%			4.00%
Debt Instrument, Unamortized Discount	2,700,000			2,700,000
Debt Maturity Date				Mar. 15, 2022
3.75% Senior Notes due 2023
Debt Instrument
Effective Interest Rate	4.32%			4.32%
Book Value	498,600,000			498,600,000			498,500,000
Fair Value	469,300,000	[2]		469,300,000	[2]		499,700,000	[2]
Stated Interest Rate	3.75%			3.75%
Debt Instrument, Unamortized Discount	1,400,000			1,400,000
Debt Maturity Date				Feb. 15, 2013
10.00% Senior Unsecured Notes due 2017
Debt Instrument
Book Value	0			0			591,900,000
Fair Value	0	[2]		0	[2]		660,800,000	[2]
Stated Interest Rate	10.00%			10.00%
Debt Instrument, Unamortized Discount	0			0
Total cash paid to redeem debt				630,000,000
Redemption Date of 10.00% Notes				Jul. 15, 2013
Loss on early extinguishment of debt				(45,200,000)
Write-off of Unamortized Discount				7,300,000
Write-off of Deferred Debt Issuance Cost				7,900,000
Early Redemption Debt Premium of 10.00% Notes				30,000,000
Extinguishment of Debt, Principal Amount				600,000,000
Debt Maturity Date				Jul. 15, 2017
4.75% Notes
Debt Instrument
Book Value	0			0			200,500,000
Fair Value	0	[2]		0	[2]		202,800,000	[2]
Stated Interest Rate	4.75%			4.75%
Extinguishment of Debt, Principal Amount				200,000,000
Debt Maturity Date				Mar. 15, 2023
4.75% Notes, Amount Retired for Cash	199,997,000			199,997,000
Conversion Rate				84.3402
Conversion of convertible notes to common stock, shares				16,900,000
Other notes payable and capitalized leases
Debt Instrument
Book Value	86,300,000			86,300,000			87,300,000
Fair Value	$ 85,800,000	[2]		$ 85,800,000	[2]		$ 90,800,000	[2]

[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 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.