Income Taxes - Components of Income Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Principal components on income tax expense:
Current taxes	$ 3,889	$ 1,989	$ 4,482
Deferred taxes	632	9,405	(23)
Income tax expense (benefit)	$ 4,521	$ 11,394	$ 4,459