Leases (Finance leases) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Ending April 1,
2020	$ 6,195
2021	7,841
2022	579
Total future payments	14,615
Less payments related to:
Maintenance	3,695
Interest	525
Present value of future minimum finance lease payments	10,395	$ 11,380
Less: Current portion	(4,041)
Total long-term finance lease payments	$ 6,354

Amounts to be paid by lessee to lessor for maintenance, insurance, and tax expenses related to the leased asset.

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Amount necessary to reduce net minimum lease payments to present value for capital leases.

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Present value of lessee's discounted obligation for lease payments from finance lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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Present value of lessee's discounted obligation for lease payments from finance lease, classified as current.

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Present value of lessee's discounted obligation for lease payments from finance lease, classified as noncurrent.

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Amount of lessee's undiscounted obligation for lease payments for finance lease.

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Amount of lessee's undiscounted obligation for lease payments for finance lease, due in next fiscal year following latest fiscal year.

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Amount of lessee's undiscounted obligation for lease payments for finance lease, due in third fiscal year following latest fiscal year.

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Amount of lessee's undiscounted obligation for lease payments for finance lease, due in second fiscal year following latest fiscal year.

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Less payments related to:

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