Significant Accounting Policies - Recast Financial Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Significant Accounting Policies [Line Items]
Revenue	$ 270,288	$ 215,390	$ 165,863
Cost of revenues	27,683	20,714	15,737
Gross profit	242,605	194,676	150,126
Research and development	69,971	47,369	36,660
Sales and marketing	168,309	133,925	105,639
General and administrative	33,460	26,801	19,822
Total operating expenses	271,740	208,095	162,121
Operating loss	(29,135)	(13,419)	(11,995)
Financial expenses, net	970	2,362	(885)
Loss before income taxes	(28,165)	(11,057)	(12,880)
Income taxes	(413)	(2,787)	(1,313)
Net loss	(28,578)	(13,844)	(14,193)
Current assets:
Prepaid expenses and other current assets	16,952	14,346
Current liabilities:
Deferred revenues	87,729	73,493
Long-term liabilities:
Deferred revenues	6,487	6,608
Other liabilities	6,781	7,807
Stockholders’ equity:
Accumulated deficit	(137,968)	(109,390)
Cash flows from operating activities:
Amortization of deferred commissions	13,185	12,591	9,525
Deferred commissions	(15,308)	(14,742)	(11,817)
Deferred revenues	14,115	20,860	11,860
Other long term liabilities	(1,025)	(405)	331
Net cash provided by operating activities	23,545	16,351	7,347
Accounting Standards Update 2014-09
Significant Accounting Policies [Line Items]
Revenue		215,390	165,863
Cost of revenues		20,714	15,737
Gross profit		194,676	150,126
Research and development		47,369	36,660
Sales and marketing		133,925	105,639
General and administrative		26,801	19,822
Total operating expenses		208,095	162,121
Operating loss		(13,419)	(11,995)
Financial expenses, net		2,362	(885)
Loss before income taxes		(11,057)	(12,880)
Income taxes		2,787	(1,313)
Net loss		(13,844)	(14,193)
Current assets:
Prepaid expenses and other current assets		14,346
Long-term assets:
Other assets		7,243
Current liabilities:
Deferred revenues		73,493
Long-term liabilities:
Deferred revenues		6,608
Other liabilities		7,807
Stockholders’ equity:
Accumulated deficit		(109,390)
Cash flows from operating activities:
Amortization of deferred commissions		12,591	9,525
Deferred commissions		(14,742)	(11,817)
Deferred revenues		20,860	11,860
Other long term liabilities		(405)	331
Net cash provided by operating activities		16,351	7,347
Previously Reported | Accounting Standards Update 2014-09
Significant Accounting Policies [Line Items]
Revenue		217,364	164,456
Cost of revenues		20,873	15,843
Gross profit		196,491	148,613
Research and development		47,369	36,660
Sales and marketing		135,896	107,825
General and administrative		26,823	19,822
Total operating expenses		210,088	164,307
Operating loss		(13,597)	(15,694)
Financial expenses, net		2,362	(885)
Loss before income taxes		(11,235)	(16,579)
Income taxes		2,459	(1,131)
Net loss		(13,694)	(17,710)
Current assets:
Prepaid expenses and other current assets		7,130
Long-term assets:
Other assets		973
Current liabilities:
Deferred revenues		73,891
Long-term liabilities:
Deferred revenues		7,034
Other liabilities		6,561
Stockholders’ equity:
Accumulated deficit		(122,454)
Cash flows from operating activities:
Amortization of deferred commissions		0	0
Deferred commissions		0	0
Deferred revenues		18,885	13,269
Other long term liabilities		(731)	147
Net cash provided by operating activities		16,351	7,347
Adjustments | Accounting Standards Update 2014-09
Significant Accounting Policies [Line Items]
Revenue		(1,974)	1,407
Cost of revenues		(159)	(106)
Gross profit		(1,815)	1,513
Research and development		0	0
Sales and marketing		(1,971)	(2,186)
General and administrative		(22)	0
Total operating expenses		(1,993)	(2,186)
Operating loss		178	3,699
Financial expenses, net		0	0
Loss before income taxes		178	3,699
Income taxes		328	(182)
Net loss		(150)	3,517
Current assets:
Prepaid expenses and other current assets		7,216
Long-term assets:
Other assets		6,270
Current liabilities:
Deferred revenues		(398)
Long-term liabilities:
Deferred revenues		(426)
Other liabilities		1,246
Stockholders’ equity:
Accumulated deficit		13,064
Cash flows from operating activities:
Amortization of deferred commissions		12,591	9,525
Deferred commissions		(14,742)	(11,817)
Deferred revenues		1,975	(1,409)
Other long term liabilities		326	184
Net cash provided by operating activities		0	0
License
Significant Accounting Policies [Line Items]
Revenue	147,613	120,341	93,243
License | Accounting Standards Update 2014-09
Significant Accounting Policies [Line Items]
Revenue		120,341	93,243
License | Previously Reported | Accounting Standards Update 2014-09
Significant Accounting Policies [Line Items]
Revenue		123,610	92,873
License | Adjustments | Accounting Standards Update 2014-09
Significant Accounting Policies [Line Items]
Revenue		(3,269)	370
Maintenance
Significant Accounting Policies [Line Items]
Revenue	$ 122,675	95,049	72,620
Maintenance | Accounting Standards Update 2014-09
Significant Accounting Policies [Line Items]
Revenue		95,049	72,620
Maintenance | Previously Reported | Accounting Standards Update 2014-09
Significant Accounting Policies [Line Items]
Revenue		93,754	71,583
Maintenance | Adjustments | Accounting Standards Update 2014-09
Significant Accounting Policies [Line Items]
Revenue		$ 1,295	$ 1,037