Lines of Credit and Financing Arrangements (Domestic Credit Facility) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Aug. 30, 2016	Nov. 13, 2014
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity			$ 650,000,000
Domestic Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity		$ 900,000,000	950,000,000
Outstanding borrowings	$ 256,000,000
Standby letters of credit	4,400,000
Line of credit, available for future borrowings	609,600,000
Maximum increase in credit facility	350,000,000
Domestic Credit Facility [Member] | Medium-term Notes [Member]
Line of Credit Facility [Line Items]
Debt instrument, face amount			$ 250,000,000
Outstanding borrowings	220,000,000
Quarterly principal repayments	7,500,000
Letter of Credit [Member]
Line of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity	100,000,000
Subfacility for Swingline Loans [Member]
Line of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity	65,000,000
Line of Credit [Member]
Line of Credit Facility [Line Items]
Minimum amount of principal or interest due on indebtedness or receivable securitization	$ 75,000,000.0