Income Taxes - Income before tax by jurisdiction (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax [Line Items]
Income before income taxes	$ (154,643)	$ 114,532	$ 105,323
Domestic Tax Authority [Member]
Income Tax [Line Items]
Income before income taxes	(179,562)	39,347	80,318
Foreign Tax Authority [Member]
Income Tax [Line Items]
Income before income taxes	$ 24,919	$ 75,185	$ 25,005