Income Taxes - Income before tax by jurisdiction (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Taxes
Income before income taxes	$ 16,633	$ (179,623)	$ 20,175	$ (163,642)
Income tax expense (benefit)	$ 7,854	$ (4,053)	$ 10,409	$ (2,335)
Effective tax rate	47.20%	2.30%	51.60%	1.40%

Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

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