Recent and Pending Accounting Standards (Details) - USD ($) $ in Thousands	Jan. 01, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings		$ 185,294		$ 191,796
Deferred revenue		(26,761)		(29,920)
Decrease to accumulated other comprehensive income		1,301		1,088
Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred revenue				(2,600)
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings			$ 400	6,800
Deferred revenue		$ 4,600		4,600
Unbilled receivables				1,300
Prepaid commissions				700
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09, Translation Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Decrease to accumulated other comprehensive income				$ 200
Scenario, Forecast | Minimum | Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Right of use asset	$ 15,000
Operating lease, liability	15,000
Scenario, Forecast | Maximum | Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Right of use asset	20,000
Operating lease, liability	$ 20,000