Debt and Other Financing (Narrative) (Details) - USD ($)	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	Jun. 30, 2016	Sep. 30, 2015	Jun. 30, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Aug. 01, 2016	Mar. 31, 2015	Jun. 30, 2009	Mar. 31, 2008	Jun. 30, 2003
Short-term Debt, Weighted Average Interest Rate	11.00%					11.00%					11.00%	4.00%
Obligations under capital leases	$ 7,600,000					$ 7,600,000					$ 7,600,000	$ 11,700,000
Write off of Deferred Debt Issuance Cost										$ 2,500,000
Gain (loss) on extinguishment of debt											1,100,000	(5,500,000)	$ 0
Accelerated deferred loss - treasury lock agreements											2,600,000
Amount outstanding under the revolving credit facility	0					0					0
Revolving credit facility draw down amount without violating covenant	354,000,000					354,000,000					354,000,000
Letters of credit outstanding	45,900,000					45,900,000					$ 45,900,000	12,900,000
Credit ratings											Our long-term credit ratings are: Moody’s ratings of Negative Outlook with Ba3 for corporate family debt, B1 for senior unsecured debt, and Ba1 for the Senior Secured Notes; S&P ratings of Positive Outlook with B for corporate family debt and senior unsecured debt and BB- for the 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					$ 250,000,000
Interest rate, stated percentage					2.375%
Prepayment percent									100.00%
Accrued Interest Paid on Extinguishment of 2.375% Notes									$ 3,100,000
Write off of Deferred Debt Issuance Cost									500,000
Gain (loss) on extinguishment of debt									(5,500,000)
Notes Make Whole Premium									$ 5,000,000
Four Point Six Zero Percent Notes, Due March Two Thousand Twenty [Member]
Principal amount of debt					$ 500,000,000
Interest rate, stated percentage					4.60%
Repayments of Debt				$ 50,100,000
Debt Instrument, Repurchase Amount			$ 40,000,000
Unamortized Debt Issuance Costs	1,400,000					1,400,000					$ 1,400,000	2,300,000
Five Point Zero Percent Notes, Due March Two Thousand Twenty-Three [Member]
Principal amount of debt					$ 500,000,000
Interest rate, stated percentage					5.00%
Debt Instrument, Repurchase Amount	11,100,000					11,100,000					11,100,000
Unamortized Debt Issuance Costs	2,300,000					2,300,000					2,300,000	2,800,000
Five Point Seven Five Percent Notes, Due March Two Thousand Eighteen [Member]
Interest rate, stated percentage																	5.75%
Repayments of Debt		$ 106,200,000		108,600,000
Debt Instrument, Repurchase Amount			35,200,000
Unamortized Debt Issuance Costs	0					0					0	400,000
Four Point Two Percent Notes, Due July Two Thousand Eighteen [Member]
Interest rate, stated percentage																		4.20%
Repayments of Debt		132,200,000		73,800,000
Debt Instrument, Repurchase Amount			44,000,000
Unamortized Debt Issuance Costs	0					0					0	200,000
Six Point Five Percent Notes, Due March Two Thousand Nineteen [Member]
Interest rate, stated percentage																6.50%
Repayments of Debt				$ 68,100,000
Debt Instrument, Repurchase Amount			44,000,000
Unamortized Debt Issuance Costs	400,000					400,000					400,000	900,000
Six Point Nine Five Percent Notes, Due March Two Thousand Forty-Three [Member]
Principal amount of debt					$ 250,000,000
Interest rate, stated percentage					6.95%
Debt Instrument, Repurchase Amount	6,200,000					6,200,000					6,200,000
Unamortized Debt Issuance Costs	2,400,000					2,400,000					2,400,000	2,500,000
Seven Point Eight Seven Five Percent Notes, Due August Two Thousand Twenty Two [Member] [Member]
Principal amount of debt														$ 500,000,000
Interest rate, stated percentage														7.875%
Unamortized Debt Issuance Costs	9,000,000					9,000,000					$ 9,000,000
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	400,000,000					400,000,000					$ 400,000,000
2013 Revolving Credit Facility [Member]
Write off of Deferred Debt Issuance Cost										$ 2,500,000
Line of credit facility												$ 1,000,000,000			$ 1,000,000,000
March 2012 Interest-Rate Swap Termination [Member]
Gain (loss) on extinguishment of debt											5,800,000.0
AIO [Member]
Letters of credit outstanding	46,000,000					46,000,000					46,000,000
Cash tender offers [Member]
Gain (loss) on extinguishment of debt							$ 3,900,000
Accelerated deferred loss - treasury lock agreements							1,200,000
Loss on extinguishment, amortization of deferred hedge gain							12,800,000
Debt repurchase, premium paid							5,800,000
Cash tender offer, deal costs							1,000,000
Write-off Deferred Debt Issuance Cost and Discount							$ 900,000
October debt repurchase [Member]
Gain (loss) on extinguishment of debt			(1,000,000)			(1,000,000)
Accelerated deferred loss - treasury lock agreements			400,000
Loss on extinguishment, amortization of deferred hedge gain			6,100,000
Debt repurchase, premium paid			6,200,000
Accrued Interest Paid on Extinguishment of Debt			1,100,000
Write-off Deferred Debt Issuance Cost and Discount			500,000
December debt repurchase [Member]
Gain (loss) on extinguishment of debt	1,100,000					1,100,000
Debt repurchase discount received	1,300,000					1,300,000					$ 1,300,000
Accrued Interest Paid on Extinguishment of Debt	300,000
Write-off Deferred Debt Issuance Cost and Discount	$ 200,000
Debt prepayment [Member]
Gain (loss) on extinguishment of debt		(2,900,000)				$ (2,900,000)
Notes Make Whole Premium		12,100,000	$ 12,100,000
Accelerated deferred loss - treasury lock agreements		1,000,000
Loss on extinguishment, amortization of deferred hedge gain		10,500,000
Accrued Interest Paid on Extinguishment of Debt		3,600,000
Write-off Deferred Debt Issuance Cost and Discount		$ 300,000