Debt and Credit Agreements - Schedule of Long-term Debt and Credit Agreements (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Unamortized debt issuance costs	$ (3,076)	$ (3,975)
Long-term debt	1,133,924	1,220,025
Current portion of long-term debt	$ 188,000	87,000
6.51% weighted-average senior notes
Debt Instrument [Line Items]
Weighted-average interest rate	6.51%
Long-term debt including unamortized debt issuance costs	$ 37,000	124,000
Current portion of long-term debt		87,000
5.58% weighted-average senior notes
Debt Instrument [Line Items]
Weighted-average interest rate	5.58%
Long-term debt including unamortized debt issuance costs	$ 175,000	175,000
Current portion of long-term debt	$ 88,000
3.65% weighted-average senior notes
Debt Instrument [Line Items]
Weighted-average interest rate	3.65%
Long-term debt including unamortized debt issuance costs	$ 925,000	925,000
Current portion of long-term debt	100,000
Revolving credit facility
Debt Instrument [Line Items]
Long-term debt including unamortized debt issuance costs	$ 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.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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