Summary of Significant Accounting Policies - Foreign Currencies (Details 8) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Other Nonoperating Income (Expense)
Foreign Currencies
Foreign currency (loss) gain	$ (1,797)	$ (2,619)	$ 3,052

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

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