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Long-Term Debt (Summary of Long-Term Debt) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Jul. 05, 2017	Jun. 30, 2017	Apr. 10, 2017	Jan. 27, 2017	Jan. 19, 2017
Debt Instrument [Line Items]
Debt obligations	$ 5,596.8		$ 5,608.7
Unamortized debt issuance costs	(65.7)		(67.8)
Carrying value of debt	5,542.5		5,537.7
Less current portion	(5.0)		(5.0)
Long-term debt, less current portion	5,537.5		5,532.7
6.00% Senior Notes due 2023 [Member]
Debt Instrument [Line Items]
Debt obligations	1,430.0		1,430.0
Unamortized premium	$ 5.3		5.5
Interest rate	6.00%
6.375% Senior Notes due 2025 [Member]
Debt Instrument [Line Items]
Debt obligations	$ 900.0		900.0
Unamortized discount	$ (13.9)		(14.3)
Interest rate	6.375%
5.75% Senior Unsecured Notes due 2027 [Member]
Debt Instrument [Line Items]
Debt obligations	$ 1,650.0	$ 300.0	1,350.0	$ 550.0	$ 800.0
Unamortized premium	$ 33.6		21.6
Interest rate	5.75%
Term Loan Facility
Debt Instrument [Line Items]
Debt obligations						$ 2,500.0
Unamortized discount	$ (13.6)		(16.0)
Carrying value of debt	1,603.2		1,912.7
Term Loan Facility due 2021 [Member]
Debt Instrument [Line Items]
Debt obligations	497.5		498.8
Term Loan Facility due 2024 [Member]
Debt Instrument [Line Items]
Debt obligations	$ 1,119.3		$ 1,429.9