Debt Schedule of Debt Instruments (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 1,590.4	$ 2,015.6
Less unamortized discount	(11.5)	(16.8)
Debt, Long-term and Short-term, Combined Amount	1,590.4	2,015.6
Total long-term debt outstanding	1,590.4	2,015.6
Revolving Credit Facility due 2022 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	0.0	0.0
6.875% Senior Notes Due 2021 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	0.0	382.4
5.375% Senior Notes Due 2022 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	465.1	500.0
5.25% Senior Notes Due 2023 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	636.8	650.0
Senior Notes Due 2026 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 500.0	$ 500.0

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Amount, after accumulated amortization, of debt discount.

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Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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