Derivatives - Fair value of derivative instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Interest rate swap contract \| Derivative instruments designated as cash flow hedges:
Derivatives, Fair Value [Line Items]
Fair value of asset derivatives	$ 0	$ 363
Interest rate swap contract \| Derivative instruments designated as cash flow hedges: \| Prepaids and other current assets
Derivatives, Fair Value [Line Items]
Fair value of asset derivatives	0	291
Interest rate swap contract \| Derivative instruments designated as cash flow hedges: \| Other assets
Derivatives, Fair Value [Line Items]
Fair value of asset derivatives	0	72
Foreign currency forward contracts \| Derivative instruments not designated as cash flow hedges:
Derivatives, Fair Value [Line Items]
Derivative assets (liabilities), at fair value, net	218	240
Foreign currency forward contracts \| Derivative instruments not designated as cash flow hedges: \| Prepaids and other current assets
Derivatives, Fair Value [Line Items]
Fair value of asset derivatives	0	240
Foreign currency forward contracts \| Derivative instruments not designated as cash flow hedges: \| Accrued liabilities
Derivatives, Fair Value [Line Items]
Fair value of liability derivatives	$ 218	$ 0

Fair values as of the balance sheet date of the net amount of all assets and liabilities resulting from contracts that meet the criteria of being accounted for as derivative instruments.

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Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

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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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