Income Taxes - Components of income before income taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Components of income before income taxes:
Domestic operations	$ 61,158	$ (3,995)	$ (48,544)
Foreign operations	90,518	93,217	80,694
Income before income taxes	$ 151,676	$ 89,222	$ 32,150