Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Income Taxes [Abstract]
Effective income tax rate	2.50%	50.70%	14.40%	31.10%
Increase in liability for uncertain tax positions			$ 1,810
Federal corporate tax rate	21.00%				35.00%
Provision of income tax expense (benefit)					$ (1,056)
Income tax expense (benefit)	$ (1,235)				(1,548)
Transition tax	$ 1,727		1,727		$ 492
Reduction in income tax expense for DPAD			$ 0	$ (1,216)