General (Details Textual)		3 Months Ended		9 Months Ended		12 Months Ended
	Aug. 21, 2020 USD ($)	Sep. 30, 2020 USD ($) subsidiary	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) subsidiary	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)	Aug. 20, 2020 USD ($)	May 11, 2020 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operations commenced date				Jan. 01, 2005
Subsidiary or equity method investee, number | subsidiary		10		10
Entity incorporation, date of incorporation				Nov. 24, 2004
Deferred revenue, revenue recognized				$ 84,630,000
Sales returns				$ 0		$ 0
Capitalized contract cost, amortization period (years)		4 years		4 years
Gain (loss) related to the effective portion of the cash flow hedges		$ 127,000	$ 361,000	$ (177,000)	$ (170,000)
Realized income on derivative instruments, net of tax		2,271,000	0	4,742,000	0
Derivative instruments not designated as hedging instruments, gain (loss), net		(876,000)	951,000	(244,000)	1,404,000
Foreign Exchange Contract
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Gain (loss) related to the effective portion of the cash flow hedges		128,000	361,000	(176,000)	(170,000)
Realized income on derivative instruments, net of tax		2,271,000		4,742,000
Ineffective hedges recognized		0	$ 0	$ 0	$ 0
Maintenance
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue, performance obligation, description of timing				one year
Revolving Credit Facility | Line of Credit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Debt instrument, term	3 years
Line of credit facility, maximum borrowing capacity	$ 70,000,000
Line of credit facility, accordion feature, increase limit	$ 90,000,000
First priority perfected lien on voting capital stock, percent	65.00%
Debt instrument, covenant, minimum available liquidity	$ 25,000,000
Letter of Credit | Line of Credit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Line of credit facility, maximum borrowing capacity	$ 15,000,000
Long-term line of credit		$ 2,439,000		$ 2,439,000
Promissory Note | Line of Credit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Line of credit facility, maximum borrowing capacity							$ 7,000,000
Credit and Security Agreement | London Interbank Offered Rate (LIBOR)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Basis spread on variable rate (percentage)	1.00%
Credit and Security Agreement | Base Rate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Basis spread on variable rate (percentage)	3.00%
Credit and Security Agreement | Eurodollar
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Basis spread on variable rate (percentage)	0.50%
2025 Senior Notes | Convertible Debt
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Interest rate, stated percentage								1.25%
Principal amount								$ 253,000,000