Summary of Significant Accounting Policies - Foreign Currencies (Details 8) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other Nonoperating Income (Expense) [Member]
Foreign Currencies
Foreign currency (loss) gain	$ (2,619)	$ 3,052	$ (3,714)

Amount before tax of foreign currency transaction realized gain (loss) recognized in the income statement.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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