Significant Accounting Policies Update (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues: Software	$ 40,628	$ 42,325	$ 83,742	$ 83,769
Operating expenses: Selling and marketing	6,093	5,329	12,562	11,251
Other comprehensive (loss) income, net of tax: foreign currency translation adjustments	(342)	82	(598)	86
Current assets: Accounts receivable, net	35,574		35,574
Current assets: Prepaid expenses and other	7,050		7,050		$ 5,752
Current liabilities: Deferred revenue	32,449		32,449		31,414
Non-current liabilities: Deferred revenue	961		961		1,063
Stockholder equity: Accumulated other comprehensive loss	(1,850)		(1,850)		(1,088)
Stockholder equity: Retained earnings	191,012		191,012		191,796
ASC 605 | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating expenses: Selling and marketing	6,198	5,329	12,228	11,251
Other comprehensive (loss) income, net of tax: foreign currency translation adjustments	(308)	82	(472)	86
Current assets: Accounts receivable, net	33,010		33,010		32,279
Current assets: Prepaid expenses and other	6,710		6,710		5,752
Current liabilities: Deferred revenue	34,667		34,667		31,414
Non-current liabilities: Deferred revenue	1,176		1,176		1,063
Stockholder equity: Accumulated other comprehensive loss	(1,604)		(1,604)		(1,088)
Stockholder equity: Retained earnings	185,429		185,429		$ 191,796
Software
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues: Software	16,970	16,686	35,815	32,270
Software | ASC 605 | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues: Software	$ 18,136	$ 16,686	$ 36,324	$ 32,270