Financing Arrangements and Debt (Narrative) (Details)	3 Months Ended
	Mar. 31, 2017 USD ($)
Line of Credit Facility [Line Items]
Capital Lease Duration	25 years
Capital lease payment duration	15 years
Capital lease expiration date	Jun. 30, 2028
Capital lease obligations, current	$ 13,000,000
Capital lease obligations, noncurrent	193,500,000
2016 Senior Unsecured Guaranteed Credity Facility [Member]
Line of Credit Facility [Line Items]
Credit facility maximum borrowing capacity	$ 1,100,000,000
Credit facility, expiration date	Aug. 01, 2019
Amount outstanding	$ 0
2016 Senior Unsecured Guaranteed Credity Facility [Member] | Eurodollar [Member]
Line of Credit Facility [Line Items]
Interest rate	5.00%
2016 Senior Unsecured Guaranteed Credity Facility [Member] | Base Rate [Member]
Line of Credit Facility [Line Items]
Interest rate	7.00%
2016 Senior Unsecured Guaranteed Credity Facility [Member] | Letter of Credit [Member]
Line of Credit Facility [Line Items]
Amount outstanding	$ 171,900,000
2011 Unscured Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Credit facility maximum borrowing capacity	630,000,000
Amount outstanding	$ 0
2011 Unscured Revolving Credit Facility [Member] | Eurodollar [Member]
Line of Credit Facility [Line Items]
Interest rate	2.45%
2011 Unscured Revolving Credit Facility [Member] | Base Rate [Member]
Line of Credit Facility [Line Items]
Interest rate	4.45%
2011 Unscured Revolving Credit Facility [Member] | Letter of Credit [Member]
Line of Credit Facility [Line Items]
Amount outstanding	$ 0