Debt and Other Financing (Narrative) (Details) - USD ($) $ in Millions	1 Months Ended					3 Months Ended				12 Months Ended
	Dec. 31, 2016	Nov. 30, 2016	Oct. 31, 2016	Aug. 31, 2016	Mar. 31, 2013	Dec. 31, 2016	Sep. 30, 2016	Sep. 30, 2015	Jun. 30, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Aug. 01, 2016	Mar. 31, 2015	Jun. 30, 2009	Mar. 31, 2008	Jun. 30, 2003
Short-term Debt, Weighted Average Interest Rate, at Point in Time	11.00%					11.00%				23.00%	11.00%
Obligations under capital leases	$ 7.6					$ 7.6				$ 4.0	$ 7.6
Gain (loss) on extinguishment of debt										0.0	1.1	$ (5.5)
Accelerated deferred loss - treasury lock agreements											2.6
Amount outstanding under the revolving credit facility										0.0
Revolving credit facility draw down amount without violating covenant										362.0
Letters of credit outstanding	45.9					45.9				$ 37.7	45.9
Credit ratings										Our long-term credit ratings are: Moody’s ratings of Stable Outlook with B1 for corporate family debt, B3 for senior unsecured debt, and Ba1 for our Senior Secured Notes; S&P ratings of Stable Outlook with B for corporate family debt and senior unsecured debt and BB- for our Senior Secured Notes; and Fitch rating of Negative Outlook with B+, each of which are below investment grade.
Two Point Three Seven Five Percent Notes, Due March Two Thousand Sixteen [Member]
Principal amount of debt					$ 250.0
Interest rate, stated percentage					2.375%
Accrued Interest Paid on Extinguishment of 2.375% Notes								$ 3.1
Write off of Deferred Debt Issuance Cost								0.5
Gain (loss) on extinguishment of debt								(5.5)
Notes Make Whole Premium								$ 5.0
Four Point Six Zero Percent Notes, Due March Two Thousand Twenty [Member]
Principal amount of debt					$ 500.0
Interest rate, stated percentage					4.60%
Repayments of Debt				$ 50.1
Debt Instrument, Repurchase Amount			$ 40.0
Unamortized Debt Issuance Costs	1.4					1.4				$ 0.9	1.4
Five Point Zero Percent Notes, Due March Two Thousand Twenty-Three [Member]
Principal amount of debt					$ 500.0
Interest rate, stated percentage					5.00%
Debt Instrument, Repurchase Amount	11.1					11.1					11.1
Unamortized Debt Issuance Costs	2.3					2.3				1.9	2.3
Five Point Seven Five Percent Notes, Due March Two Thousand Eighteen [Member]
Interest rate, stated percentage																5.75%
Repayments of Debt		$ 106.2		108.6
Debt Instrument, Repurchase Amount			35.2
Four Point Two Percent Notes, Due July Two Thousand Eighteen [Member]
Interest rate, stated percentage																	4.20%
Repayments of Debt		132.2		73.8
Debt Instrument, Repurchase Amount			44.0
Six Point Five Percent Notes, Due March Two Thousand Nineteen [Member]
Interest rate, stated percentage															6.50%
Repayments of Debt				$ 68.1
Debt Instrument, Repurchase Amount			44.0
Unamortized Debt Issuance Costs	0.4					0.4				0.3	0.4
Six Point Nine Five Percent Notes, Due March Two Thousand Forty-Three [Member]
Principal amount of debt					$ 250.0
Interest rate, stated percentage					6.95%
Debt Instrument, Repurchase Amount	6.2					6.2					6.2
Unamortized Debt Issuance Costs	2.4					2.4				2.2	2.4
Seven Point Eight Seven Five Percent Notes, Due August Two Thousand Twenty Two [Member] [Member]
Principal amount of debt													$ 500.0
Interest rate, stated percentage													7.875%
Unamortized Debt Issuance Costs	9.0					9.0				$ 7.4	9.0
2013 Notes [Member]
Debt Instrument, Interest Rate Terms										The indenture governing the 2013 Notes contains interest rate adjustment provisions depending on the long-term credit ratings assigned to the 2013 Notes with S&P and Moody's. As described in the indenture, the interest rates on the 2013 Notes increase by .25% for each one-notch downgrade below investment grade on each of our long-term credit ratings assigned to the 2013 Notes by S&P or Moody's. These adjustments are limited to a total increase of 2% above the respective interest rates in effect on the date of issuance of the 2013 Notes.
2013 Notes [Member] | Notes Payable [Member]
Debt Instrument, Covenant, Increase In Interest Rate For Every One-Notch Downgrade Of Long-Term Credit Ratings Below Investment Grade					0.25%
Debt Instrument, Covenant, Maximum Aggregate Increase In Interest Rate Related To Downgrade Of Long-Term Credit Ratings Below Investment Grade					2.00%
All Notes Outstanding, Except 4.20% Notes [Member] | Notes Payable [Member]
Debt Instrument, Covenant, Minimum Required Offer To Repurchase, Percentage Of Aggregate Principal Amount										101.00%
Revolving Credit Facility [Member]
Debt Instrument, Interest Rate Terms										Borrowings under the 2015 facility bear interest, at our option, at a rate per annum equal to LIBOR plus 250 basis points or a floating base rate plus 150 basis points, in each case subject to adjustment based upon a leverage-based pricing grid.
Line of credit facility										$ 400.0
2013 Revolving Credit Facility [Member]
Write off of Deferred Debt Issuance Cost									$ 2.5
Line of credit facility														$ 1,000.0
March 2012 Interest-Rate Swap Termination [Member]
Gain (loss) on extinguishment of debt											5.8
AIO [Member]
Letters of credit outstanding										$ 38.0
Cash tender offers [Member]
Gain (loss) on extinguishment of debt							$ 3.9
Accelerated deferred loss - treasury lock agreements							1.2
Loss on extinguishment, amortization of deferred hedge gain							12.8
Debt repurchase, premium paid							5.8
Cash tender offer, deal costs							1.0
Write-off Deferred Debt Issuance Cost and Discount							$ 0.9
October debt repurchase [Member]
Gain (loss) on extinguishment of debt			(1.0)			(1.0)
Accelerated deferred loss - treasury lock agreements			0.4
Loss on extinguishment, amortization of deferred hedge gain			6.1
Debt repurchase, premium paid			6.2
Accrued Interest Paid on Extinguishment of Debt			1.1
Write-off Deferred Debt Issuance Cost and Discount			0.5
December debt repurchase [Member]
Gain (loss) on extinguishment of debt	1.1					1.1
Debt repurchase discount received	1.3					1.3					$ 1.3
Accrued Interest Paid on Extinguishment of Debt	0.3
Write-off Deferred Debt Issuance Cost and Discount	$ 0.2
Debt prepayment [Member]
Gain (loss) on extinguishment of debt		(2.9)				$ (2.9)
Notes Make Whole Premium		12.1	$ 12.1
Accelerated deferred loss - treasury lock agreements		1.0
Loss on extinguishment, amortization of deferred hedge gain		10.5
Accrued Interest Paid on Extinguishment of Debt		3.6
Write-off Deferred Debt Issuance Cost and Discount		$ 0.3