Income Taxes - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating Loss Carryforwards [Line Items]
Valuation recorded		$ 6,900
Net operating loss carryforwards	$ 8,093	18,083	$ 8,093
Unrecognized tax benefits	4,924	1,921	4,924	$ 4,240
Decrease in unrecognized tax benefits that is reasonably possible		1,000
Settlements of audit		2,963	0
Decrease in federal deferred tax provision upon remeasurement of net deferred taxes at newly enacted rate, provisional estimate	10,100
Federal deferred tax benefit upon remeasurement of valuation allowance at newly enacted rate, provisional estimate	12,600
Federal deferred tax benefit for indefinite lived deferred tax liabilities, provisional estimate	$ 2,000
Percentage of indefinite-lived deferred tax liabilities (percent)	80.00%
State deferred tax provision	$ 1,200	(28)	(1,144)	$ 99
Federal
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards		73,000
Operating loss carryforwards generated in taxable years ending on or before December 31 2017	$ 32,800	32,800	$ 32,800
Net operating loss carryforwards		74,200
Net operating loss carryforwards, not subject to expiration		$ 39,200
Operating loss carryforwards, period of carryforward (in years)		20 years
Federal | Expiration between 2023 and 2026
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards, subject to expiration		$ 6,000
Federal | Expiration between 2036 and 2037
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards, subject to expiration		28,900
Federal | Proficient [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards		5,100
Foreign | Australian Taxation Office
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards		5,300
Foreign | Israel Tax Authority
Operating Loss Carryforwards [Line Items]
Settlements of audit		$ 3,000