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 Tax Disclosure [Abstract]
Liability for unrecognized tax benefits	$ 6,067		$ 6,067
Unrecognized tax benefits, income tax penalties and interest accrued	489		489
Unrecognized tax benefits that would impact the effective tax rate	5,842		$ 5,842
Federal Statutory Income Tax Rate, Historical					35.00%
Tax Cuts and Jobs Act of 2017 Corporate Federal Tax Rate			21.00%
Effective Income Tax Rate Reconciliation, Tax Cuts And Jobs Act Of 2017, Transition Tax On Accumulated Foreign Earnings, Percent			(1.30%)
Income Tax Expense	$ 158	$ 731	$ 1,598	$ 385
Effective Income Tax Rate Reconciliation, Percent	1.60%		5.80%
Tax Cuts And Jobs Act Of 2017, Transition Tax Liability For Accumulated Foreign Earnings, Income Tax Expense			$ (362)
Other Tax Benefits			$ 3,568
Income Tax Examination [Line Items]
Income Tax Examination, Year under Examination			2015
Minimum
Income Tax Examination [Line Items]
Income Tax Examination, Year under Examination			2014
Maximum
Income Tax Examination [Line Items]
Income Tax Examination, Year under Examination			2016