Recent and Pending Accounting Standards (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings	$ 191,012		$ 191,796
Decrease to deferred revenue	(33,410)		(32,477)
Decrease to accumulated other comprehensive income	1,850		1,088
ASC 606 | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings			6,400
Decrease to deferred revenue	$ 4,200		4,200
Decrease to accumulated other comprehensive income		$ (1,500)	(1,100)
Unbilled receivables			1,300
Prepaid commissions			700
ASC 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