Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2017	Jun. 30, 2018	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Income Taxes [Line Items]
Income tax expense (benefit)	$ 67		$ 85		$ 112	$ (2,459)
Effective income tax rate (as a percent)	1.00%		2.00%		1.00%	34.00%
U.S. federal statutory rate (as a percent)	21.00%				21.00%		34.00%
One-time transition tax							$ 9,000
Valuation allowance decrease	$ 100	$ 400		$ 400	$ 100		9,000
Net tax expense or benefit							0
Transition tax, unrepatriated foreign earnings	100	$ 400		$ 400	100
AMT credit carryforwards, one-time tax benefit							400
AMT valuation allowance decrease							400
Tax benefit arising from Tax Act							200
Unrepatriated foreign earnings, incomplete accounting for tax effect	0				0
State
Income Taxes [Line Items]
Net operating loss							67,800
Tax credit carryforwards							2,800
Federal
Income Taxes [Line Items]
Income tax examination, deferred tax expense	100				100
Income tax examination, deferred tax benefit	100				100
Income tax examination, net tax impact	0				0
Tax credit carryforwards							6,600
Federal | Before measurement period adjustment
Income Taxes [Line Items]
Net operating loss							66,700
Federal | Measurement period adjustment
Income Taxes [Line Items]
Net operating loss	$ (600)				$ (600)		(2,200)
Federal | After measurement period adjustment
Income Taxes [Line Items]
Net operating loss							63,900
Federal | Amount after transition tax pursuant to Tax Cuts and Jobs Act
Income Taxes [Line Items]
Net operating loss							$ 64,500