Debt (Details) - USD ($) $ in Millions	1 Months Ended			3 Months Ended		9 Months Ended
	Nov. 30, 2016	Aug. 31, 2016	Aug. 31, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Aug. 01, 2016	Mar. 31, 2013	Jun. 30, 2009	Mar. 31, 2008	Jun. 30, 2003	Mar. 31, 2003
Debt Instrument [Line Items]
Amount outstanding under revolving credit facility				$ 0.0		$ 0.0
Revolving credit facility draw down amount without violating covenant				130.0		$ 130.0
Repayments of Debt	$ 238.4	$ 300.6
Debt Instrument, Repurchase Amount								$ 180.5
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 the Senior Secured Notes; S&P ratings of Stable 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.
Gain on Extinguishment of Debt				0.0	$ 3.9	$ 0.0	$ 3.9
Loss on extinguishment, amortization of deferred hedge gain					12.8
Debt repurchase, premium paid					5.8
Deferred loss - treasury lock agreements					1.2
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility				400.0		$ 400.0
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.
2013 Notes [Member]
Debt Instrument [Line Items]
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 by 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.
Six Point Five Percent Notes Due March Two Thousand Nineteen [Member]
Debt Instrument [Line Items]
Repayments of Other Long-term Debt		68.1
Debt Instrument, Face Amount												$ 350.0
Debt Instrument, Interest Rate, Stated Percentage											6.50%	6.50%
Notes Payable, Other Payables [Member]
Debt Instrument [Line Items]
Debt Instrument, Covenant, Minimum Required Offer To Repurchase, Percentage Of Aggregate Principal Amount						101.00%
Five Point Seven Five Percent Notes, Due March Two Thousand Eighteen [Member]
Debt Instrument [Line Items]
Repayments of Other Long-term Debt		108.6
Debt Instrument, Interest Rate, Stated Percentage												5.75%
Cash tender offer, deal costs					1.0
Write off of Deferred Debt Issuance Cost					$ 0.9
Four Point Two Percent Notes, Due July Two Thousand Eighteen [Member]
Debt Instrument [Line Items]
Repayments of Other Long-term Debt		73.8
Debt Instrument, Interest Rate, Stated Percentage													4.20%	4.20%
Two Point Three Seven Five Percent Notes, Due March Two Thousand Sixteen [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount										$ 250.0
Debt Instrument, Interest Rate, Stated Percentage										2.375%
Repayments of Debt			$ 250.0
Four Point Six Zero Percent Notes, Due March Two Thousand Twenty [Member]
Debt Instrument [Line Items]
Repayments of Other Long-term Debt		$ 0.0
Debt Instrument, Face Amount										$ 500.0
Debt Instrument, Interest Rate, Stated Percentage										4.60%
Five Point Zero Percent Notes, Due March Two Thousand Twenty-Three [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount										$ 500.0
Debt Instrument, Interest Rate, Stated Percentage										5.00%
Six Point Nine Five Percent Notes, Due March Two Thousand Forty-Three [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount										$ 250.0
Debt Instrument, Interest Rate, Stated Percentage										6.95%
Seven Point Eight Seven Five Percent Notes, Due August Two Thousand Twenty Two [Domain]
Debt Instrument [Line Items]
Debt Instrument, Face Amount									$ 500.0
Debt Instrument, Interest Rate, Stated Percentage									7.875%
AIO [Member]
Debt Instrument [Line Items]
Standby letters of credit, recorded liability				$ 39.0		$ 39.0