Debt - Maturities of Long-Term Debt (Details)	Mar. 31, 2019 USD ($)
Debt Instrument [Line Items]
2020	$ 209,000,000
2021	7,000,000
2022	710,000,000
2023	10,000,000
2024	70,000,000
Thereafter	330,000,000
Long-term Debt, Gross	1,336,000,000
Senior Notes \| 5.375% Notes
Debt Instrument [Line Items]
2020	0
2021	0
2022	700,000,000
2023	0
2024	0
Thereafter	0
Long-term Debt, Gross	700,000,000
Senior Notes \| 4.875% Notes
Debt Instrument [Line Items]
2020	0
2021	0
2022	0
2023	0
2024	0
Thereafter	330,000,000
Long-term Debt, Gross	330,000,000
Convertible Notes \| 1.125% Convertible Notes
Debt Instrument [Line Items]
2020	206,000,000
2021	0
2022	0
2023	0
2024	0
Thereafter	0
Long-term Debt, Gross	206,000,000
Line of Credit \| Term Loan
Debt Instrument [Line Items]
2020	3,000,000
2021	7,000,000
2022	10,000,000
2023	10,000,000
2024	70,000,000
Thereafter	0
Long-term Debt, Gross	$ 100,000,000

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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