Long Term Debt and Financing Arrangements - Narrative (Details) - USD ($)	1 Months Ended		3 Months Ended
	Feb. 28, 2018	Jan. 31, 2018	Sep. 30, 2018	Feb. 02, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Short-term debt and current portion of long-term debt			$ 130,300,000		$ 68,100,000
Senior Notes | Notes 2028 Term
Debt Instrument [Line Items]
Face amount	$ 450,000,000			$ 450,000,000
Interest rate, stated percentage	3.50%		3.50%	3.50%
Long-term debt borrowings, net	$ 442,600,000
Line of Credit | Term Loan Agreement
Debt Instrument [Line Items]
Line of credit, maximum borrowing capacity		$ 500,000,000		$ 500,000,000
Amortization percentage, equal quarterly installments, year one				5.00%
Amortization percentage, equal quarterly installments, year two				5.00%
Amortization percentage, equal quarterly installments, year three				7.50%
Amortization percentage, equal quarterly installments, year four				10.00%
Amortization percentage, equal quarterly installments, year five				10.00%
Payment against debt			$ 100,000,000
Revolving Credit Facility | Line of Credit | Credit Agreement
Debt Instrument [Line Items]
Line of credit, maximum borrowing capacity		$ 750,000,000
Line of credit facility covenants maximum debt to capitalization percentage		65.00%
Debt term		5 years
Line of credit facility, accordion feature, higher borrowing capacity option		$ 1,250,000,000.000