Debt and Credit Agreements - Schedule of Debt (Details) - USD ($)	Mar. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Unamortized debt issuance costs	$ (3,740,000)	$ (3,975,000)
Long-term debt	1,220,260,000	1,220,025,000
Current portion of long-term debt	175,000,000	87,000,000
6.51% weighted-average senior notes
Debt Instrument [Line Items]
Total debt	$ 124,000,000	124,000,000
Weighted average interest rate	6.51%
Current portion of long-term debt	$ 87,000,000.0	87,000,000
5.58% weighted-average senior notes
Debt Instrument [Line Items]
Total debt	$ 175,000,000	175,000,000
Weighted average interest rate	5.58%
Current portion of long-term debt	$ 88,000,000.0
3.65% weighted-average senior notes
Debt Instrument [Line Items]
Total debt	$ 925,000,000	925,000,000
Weighted average interest rate	3.65%
Revolving credit facility
Debt Instrument [Line Items]
Total debt	$ 0	$ 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 issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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