Debt (Details) - USD ($)	3 Months Ended		6 Months Ended
	Sep. 30, 2015	Jun. 30, 2015	Jun. 30, 2015	Jun. 30, 2013	Jun. 30, 2009	Mar. 31, 2008	Jun. 30, 2003
Debt Instrument [Line Items]
Write off of Deferred Debt Issuance Cost		$ 2,500,000
Amount outstanding under revolving credit facility		0	$ 0
Revolving credit facility draw down amount without violating covenant		400,000,000	$ 400,000,000
Credit ratings			Our long-term credit ratings are Ba2 (Negative Outlook) for corporate family debt, and Ba3 (Negative Outlook) for senior unsecured debt, with Moody's; B+ (Stable Outlook) with S&P; and BB- (Negative Outlook) with Fitch, which are below investment grade.
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility		400,000,000	$ 400,000,000
Debt Instrument, Interest Rate Terms			Borrowings under the 2015 revolving credit 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 Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility		1,000,000,000	$ 1,000,000,000
Amount drawn under credit facility		0	0
Termination penalty on revolving credit facility		$ 0	$ 0
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 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.
Six Point Five Percent Notes Due March Two Thousand Nineteen [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount					$ 350,000,000
Debt Instrument, Interest Rate, Stated Percentage					6.50%
Five Point Seven Five Percent Notes, Due March Two Thousand Eighteen [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount						$ 250,000,000
Debt Instrument, Interest Rate, Stated Percentage						5.75%
Four Point Two Percent Notes, Due July Two Thousand Eighteen [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount							$ 250,000,000
Debt Instrument, Interest Rate, Stated Percentage							4.20%
Two Point Three Seven Five Percent Notes, Due March Two Thousand Sixteen [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount				$ 250,000,000
Debt Instrument, Interest Rate, Stated Percentage				2.375%
2013 Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Increase (Decrease)			1.75%
Debt Instrument, Interest Rate, Increase (Decrease) effective March 15, 2015			0.75%
Debt Instrument, Interest Rate, Increase (Decrease) effective September 15, 2015			1.00%
Four Point Six Zero Percent Notes, Due March Two Thousand Twenty [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount				$ 500,000,000
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				$ 500,000,000
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				$ 250,000,000
Debt Instrument, Interest Rate, Stated Percentage				6.95%
Subsequent Event [Member] | Two Point Three Seven Five Percent Notes, Due March Two Thousand Sixteen [Member]
Debt Instrument [Line Items]
Prepayment percent	100.00%
Accrued Interest To Be Paid	$ 3,000,000
Estimated make whole premium to be paid	5,000,000
Estimated loss on extinguishment of debt	$ 5,000,000