Fair Value Measurements - Carrying Amount and Fair Value of Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair value disclosures
Long-term debt	$ 1,133,924	$ 1,220,025
Current maturities	(188,000)	(87,000)
Long-term debt, excluding current maturities	945,924	1,133,025
Carrying Amount
Fair value disclosures
Long-term debt	1,133,924	1,220,025
Current maturities	(188,000)	(87,000)
Long-term debt, excluding current maturities	945,924	1,133,025
Estimated Fair Value
Fair value disclosures
Long-term debt	1,213,811	1,260,259
Current maturities	(189,332)	(88,704)
Long-term debt, excluding current maturities	$ 1,024,479	$ 1,171,555

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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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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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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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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