Income Taxes (Details) - USD ($)	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 Tax Disclosure [Abstract]
Income tax (benefit) expense	$ (1,764,000)	$ 2,389,000	$ 5,668,000	$ 7,505,000
Effective income tax rate	48.50%	47.70%	24.40%	(38.20%)
Increase in effective tax rate due to benefits from tax credit and reversal of provisional estimate for transition tax	14.80%
Decrease in effective tax rate due to change in U.S. federal statutory rate	$ 0.14
Provisional discrete net tax benefit recorded as result of changes in tax law					$ 73,500,000
Provisional tax expense (benefit) for one-time transition tax recorded as result of changes in tax law	(1,400,000)				1,400,000
Provisional tax expense (benefit) recorded for revaluation of deferred tax assets and liabilities as result of changes in tax law	$ 1,300,000				$ (74,900,000)