Amount due from customers or clients, within one year of the balance sheet date (or the normal operating cycle, whichever is longer), for goods or services (including trade receivables) that have been delivered or sold in the normal course of business, reduced to the estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130549-203045

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(3))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Revenue - Impacts on financial statements (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2018
Current assets
Accounts receivable, net of allowance	$ 59,631				$ 48,126				$ 59,631	$ 48,126
Contract asset	7,962								7,962
Other current assets	5,705				5,501				5,705	5,501
Total current assets	191,956				227,937				191,956	227,937
Deferred income taxes	5,601				5,460				5,601	5,460
Contract assets - non-current	3,316								3,316
Other assets	8,400				5,229				8,400	5,229
Total assets	352,826				337,622				352,826	337,622
Current liabilities
Deferred revenue	33,633				33,295				33,633	33,295
Short-term income taxes payable	6,905				3,673				6,905	3,673
Other accrued expenses	9,323				7,746				9,323	7,746
Total current liabilities	72,357				66,153				72,357	66,153
Deferred revenue - non-current	10,672				7,019				10,672	7,019
Deferred income taxes	2,661				7,753				2,661	7,753
Total liabilities	100,385				99,692				100,385	99,692
Stockholders' equity
Accumulated income	172,378				156,151				172,378	156,151
Total stockholders' equity	252,441				237,930				252,441	237,930
Total liabilities and stockholders' equity	352,826				337,622				352,826	337,622
Revenue
Total revenue	64,799	$ 52,495	$ 49,554	$ 45,432	54,506	$ 51,126	$ 45,694	$ 41,965	212,280	193,291	$ 192,304
Cost of goods sold
Total cost of goods sold									64,813	58,777	61,647
Gross profit	42,246	34,543	35,981	34,697	35,908	36,646	32,048	29,912	147,467	134,514	130,657
Operating costs
Sales and marketing									63,805	58,994	57,347
Total operating costs	38,145	37,657	38,592	33,049	34,730	31,534	32,448	29,610	147,443	128,322	121,058
Operating income	4,101	(3,114)	(2,611)	1,648	1,178	5,112	(400)	302	24	6,192	9,599
Income (loss) before taxes									3,553	8,381	11,377
Provision (benefit) for income taxes	650	(1,702)	(872)	629	27,786	2,558	313	233	(293)	30,780	863
Net income (loss)	$ 3,964	$ (908)	$ (1,002)	$ 1,792	$ (25,837)	$ 2,755	$ 110	$ 573	$ 3,846	$ (22,399)	$ 10,514
Basic (in dollars per share)	$ 0.10	$ (0.02)	$ (0.03)	$ 0.04	$ (0.65)	$ 0.07	$ 0.00	$ 0.01	$ 0.10	$ (0.56)	$ 0.27
Diluted (in dollars per share)	$ 0.10	$ (0.02)	$ (0.03)	$ 0.04	$ (0.65)	$ 0.07	$ 0.00	$ 0.01	$ 0.10	$ (0.56)	$ 0.27
Product and license
Revenue
Total revenue									$ 152,977	$ 147,257	$ 156,057
Cost of goods sold
Total cost of goods sold									50,706	48,333	53,191
Service and other
Revenue
Total revenue									59,303	46,034	36,247
Cost of goods sold
Total cost of goods sold									14,107	$ 10,444	$ 8,456
ASU 2014-09
Stockholders' equity
Accumulated income												$ 11,900
ASU 2014-09 \| Adjustments
Current assets
Accounts receivable, net of allowance	$ (331)								(331)
Contract asset	(7,962)								(7,962)
Other current assets	(703)								(703)
Total current assets	(8,996)								(8,996)
Deferred income taxes	587								587
Contract assets - non-current	(3,316)								(3,316)
Other assets	(289)								(289)
Total assets	(12,014)								(12,014)
Current liabilities
Deferred revenue	3,019								3,019
Short-term income taxes payable	(1,209)								(1,209)
Other accrued expenses	(116)								(116)
Total current liabilities	1,694								1,694
Deferred revenue - non-current	3,391								3,391
Deferred income taxes	(424)								(424)
Total liabilities	4,661								4,661
Stockholders' equity
Accumulated income	(16,675)								(16,675)
Total stockholders' equity	(16,675)								(16,675)
Total liabilities and stockholders' equity	(12,014)								(12,014)
Revenue
Total revenue									(3,407)
Cost of goods sold
Total cost of goods sold									605
Gross profit									(4,012)
Operating costs
Sales and marketing									1,108
Total operating costs									1,108
Operating income									(5,120)
Income (loss) before taxes									(5,120)
Provision (benefit) for income taxes									(365)
Net income (loss)									(4,755)
ASU 2014-09 \| Balances without the adoption of Topic 606
Current assets
Accounts receivable, net of allowance	59,300								59,300
Other current assets	5,002								5,002
Total current assets	182,960								182,960
Deferred income taxes	6,188								6,188
Other assets	8,111								8,111
Total assets	340,812								340,812
Current liabilities
Deferred revenue	36,652								36,652
Short-term income taxes payable	5,696								5,696
Other accrued expenses	9,207								9,207
Total current liabilities	74,051								74,051
Deferred revenue - non-current	14,063								14,063
Deferred income taxes	2,237								2,237
Total liabilities	105,046								105,046
Stockholders' equity
Accumulated income	155,703								155,703
Total stockholders' equity	235,766								235,766
Total liabilities and stockholders' equity	$ 340,812								340,812
Revenue
Total revenue									208,873
Cost of goods sold
Total cost of goods sold									65,418
Gross profit									143,455
Operating costs
Sales and marketing									64,913
Total operating costs									148,551
Operating income									(5,096)
Income (loss) before taxes									(1,567)
Provision (benefit) for income taxes									(658)
Net income (loss)									$ (909)
Basic (in dollars per share)									$ (0.02)
Diluted (in dollars per share)									$ (0.02)
ASU 2014-09 \| Product and license \| Adjustments
Revenue
Total revenue									$ 2,365
Cost of goods sold
Total cost of goods sold									605
ASU 2014-09 \| Product and license \| Balances without the adoption of Topic 606
Revenue
Total revenue									155,342
Cost of goods sold
Total cost of goods sold									51,311
ASU 2014-09 \| Service and other \| Adjustments
Revenue
Total revenue									(5,772)
ASU 2014-09 \| Service and other \| Balances without the adoption of Topic 606
Revenue
Total revenue									53,531
Cost of goods sold
Total cost of goods sold									$ 14,107