| Leases (Maturity Schedule) (Details) - USD ($) $ in Thousands | Mar. 31, 2021 | Dec. 31, 2020 | Mar. 31, 2020 | 
|---|---|---|---|
| Lessee, Operating Lease, Liability, Payment, Due [Abstract] | |||
| Less: current obligations | $ (81,308) | $ (65,466) | $ (64,456) | 
| Operating Lease, Liability, Noncurrent | $ 356,766 | $ 353,181 | $ 364,300 | 
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- References No definition available. 
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| X | ||||||||||
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- Definition Present value of lessee's discounted obligation for lease payments from operating lease, classified as current. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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| X | ||||||||||
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- Definition Present value of lessee's discounted obligation for lease payments from operating lease, classified as noncurrent. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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