Revenue Recognition - Financial Statement Impact of Adoption (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017	Apr. 01, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	$ 27,000				$ 16,389				$ 27,000	$ 16,389		$ 19,513
Contract assets	2,921				0				2,921	0		4,583
Prepaid Expense, Current	6,272				5,593				6,272	5,593
Prepaid expenses and other current assets												5,097
Other non-current assets	6,118				2,484				6,118	2,484		4,893
Contract with Customer, Liability, Current	38,669				26,820				38,669	26,820
Contract liabilities												33,826
Retained earnings	93,051				103,601				93,051	103,601		106,215
Net revenue	36,618	$ 36,014	$ 34,203	$ 34,007	32,056	$ 31,310	$ 30,129	$ 33,865	140,842	127,360	$ 127,678
Sales and marketing									19,646	18,075	20,823
Net loss									(13,164)
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	23,046				16,389				23,046	16,389
Contract assets	0				0				0	0
Prepaid expenses and other current assets	6,665				5,593				6,665	5,593
Other non-current assets	3,152				2,484				3,152	2,484
Contract liabilities	32,343				26,820				32,343	26,820
Retained earnings	89,929				$ 103,601				89,929	103,601
Net revenue									140,997
Sales and marketing									20,309
Net loss									(13,672)
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	3,954								3,954			3,124
Contract assets	2,921								2,921			4,583
Prepaid expenses and other current assets	(393)								(393)			(496)
Other non-current assets	2,966								2,966			2,409
Contract liabilities	6,326								6,326			7,006
Retained earnings	$ 3,122								3,122			$ 2,614
Net revenue									(155)
Sales and marketing									(663)
Net loss									(508)
Products
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenue									39,003	33,699	38,339
Products | Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenue									37,466
Products | Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenue									1,537
Support, Maintenance And Subscription Services [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenue									75,496	69,068	63,308
Support, Maintenance And Subscription Services [Member] | Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenue									76,330
Support, Maintenance And Subscription Services [Member] | Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenue									(834)
Professional services
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenue									26,343	$ 24,593	$ 26,031
Professional services | Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenue									27,201
Professional services | Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenue									$ (858)