Leases (Breakdown of Lease Expense) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2019
Leases
Operating lease cost	$ 4,096	$ 13,379
Amortization of leased assets	2,103	5,555
Interest on lease liabilities	211	565
Short-term lease cost	1,889	6,964
Sublease income	(150)	(447)
Lease expense	$ 8,149	$ 26,016

Amount of interest expense on finance lease liability.

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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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- Definition

Amount of amortization expense attributable to right-of-use asset from finance lease.

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- Definition

Amount of lease cost recognized by lessee for lease contract.

+ References

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- Definition

Amount of single lease cost, calculated by allocation of remaining cost of lease over remaining lease term. Includes, but is not limited to, single lease cost, after impairment of right-of-use asset, calculated by amortization of remaining right-of-use asset and accretion of lease liability.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
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Amount of short-term lease cost, excluding expense for lease with term of one month or less.

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- Definition

Amount of sublease income excluding finance and operating lease expense.

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