Debt and Credit Facilities (Narrative) (Details) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Debt Instrument [Line Items]
Long-term Debt, Description		1200.0
Principal amount of notes	$ 400,000,000	$ 400,000,000
Borrowings from revolving facility	165,000,000	165,000,000	$ 0
Write off of Deferred Debt Issuance Cost	400,000
Payments of Debt Issuance Costs	1,200,000	3,000,000	300,000
Debt Issuance Costs, Gross	2,600,000	2,600,000
Payments of long-term debt		23,500,000	$ 53,600,000
Letters of credit outstanding amount	18,000,000	18,000,000
Term Loan Facility due 2022 [Member]
Debt Instrument [Line Items]
Long-term debt	700,000,000	700,000,000		$ 0
Term Loan A Facility Due 2022 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 0	$ 0		879,800,000
Term Loan Facility due 2022 [Member] | Term Loan Facility due 2022 [Member]
Debt Instrument [Line Items]
Debt, Weighted Average Interest Rate	2.95%	2.95%
Unamortized debt issuance costs, net [Member] | Unamortized debt issuance costs, net [Member]
Debt Instrument [Line Items]
Unamortized debt issuance costs, net	$ (19,000,000)	$ (19,000,000)		(18,300,000)
5.875% Senior Notes Due 2023 [Member] | 5.875% Senior Notes Due 2023 [Member]
Debt Instrument [Line Items]
Principal amount of notes	$ 300,000,000.0	$ 300,000,000.0
5.875% Senior notes due 2023	5.875%	5.875%
Long-term debt	$ 300,000,000	$ 300,000,000		300,000,000
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Long-term debt	165,000,000	165,000,000		0
Revolving Credit Facility [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility, borrowing capacity	500,000,000	500,000,000
Term Loan A Facility Due 2022 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 700,000,000	$ 700,000,000
Senior Notes [Member] | 5.75% Senior Notes Due 2021 [Member]
Debt Instrument [Line Items]
Debt, Weighted Average Interest Rate	5.75%	5.75%
5.75% Senior Notes Due 2021 [Member] | 5.75% Senior Notes Due 2021 [Member]
Debt Instrument [Line Items]
Principal amount of notes	$ 300,000,000	$ 300,000,000
5.875% Senior notes due 2023	5.75%	5.75%
Long-term debt	$ 300,000,000	$ 300,000,000		$ 300,000,000
Subsidiaries [Member] | Senior Notes [Member] | 5.875% Senior Notes Due 2023 [Member]
Debt Instrument [Line Items]
Debt, Weighted Average Interest Rate	5.875%	5.875%
Interest Rate Swap [Member]
Debt Instrument [Line Items]
Principal amount of notes	$ 250,000,000	$ 250,000,000