Presentation and Summary of Significant Accounting Policies - Summary of Effect of Adopting Topic 606 on Condensed Consolidated Statement of Operations (Detail) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended
		Jul. 31, 2018	Jul. 31, 2017
Revenues
Revenues		$ 27,399	$ 26,886
Cost of revenues:
Cost of revenues		13,647	11,661
Gross margin		13,752	15,225
Research and development		3,675	2,507
Sales and marketing		5,180	5,233
General and administrative		4,193	3,515
Amortization of acquisition-related intangibles		97	348
Total operating expenses		13,145	11,603
Operating income		607	3,622
Other income:
Interest income		504	363
Other, net		249	236
Earnings before income taxes		1,360	4,221
Income tax (benefit) expense		(25)	1,496
Net earnings		$ 1,385	$ 2,725
Earnings per common share:
Basic	[1]	$ 0.05	$ 0.09
Diluted	[1]	$ 0.04	$ 0.09
Balances under Prior GAAP
Revenues
Revenues		$ 27,015
Cost of revenues:
Cost of revenues		13,647
Gross margin		13,368
Research and development		3,675
Sales and marketing		5,210
General and administrative		4,193
Amortization of acquisition-related intangibles		97
Total operating expenses		13,175
Operating income		193
Other income:
Interest income		504
Other, net		249
Earnings before income taxes		946
Income tax (benefit) expense		(101)
Net earnings		$ 1,047
Earnings per common share:
Basic		$ 0.04
Diluted		$ 0.03
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Revenues
Revenues		$ (384)
Cost of revenues:
Gross margin		(384)
Sales and marketing		30
Total operating expenses		30
Operating income		(414)
Other income:
Earnings before income taxes		(414)
Income tax (benefit) expense		76
Net earnings		$ (338)
Earnings per common share:
Basic		$ (0.01)
Diluted		$ (0.01)
License
Revenues
Revenues		$ 1,702	$ 4,015
Cost of revenues:
Cost of revenues		1,714	1,507
License | Balances under Prior GAAP
Revenues
Revenues		1,256
Cost of revenues:
Cost of revenues		1,714
License | Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Revenues
Revenues		(446)
Subscription Fees
Revenues
Revenues		3,168	1,619
Cost of revenues:
Cost of revenues		1,068	681
Subscription Fees | Balances under Prior GAAP
Revenues
Revenues		3,170
Cost of revenues:
Cost of revenues		1,068
Subscription Fees | Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Revenues
Revenues		2
Professional Services and Other
Revenues
Revenues		11,008	10,424
Cost of revenues:
Cost of revenues		8,667	7,246
Professional Services and Other | Balances under Prior GAAP
Revenues
Revenues		11,068
Cost of revenues:
Cost of revenues		8,667
Professional Services and Other | Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Revenues
Revenues		60
Maintenance
Revenues
Revenues		11,521	10,828
Cost of revenues:
Cost of revenues		2,198	$ 2,227
Maintenance | Balances under Prior GAAP
Revenues
Revenues		11,521
Cost of revenues:
Cost of revenues		$ 2,198

[1] Basic per share amounts are the same for Class A and Class B Common Shares. Diluted per share amounts for Class A Common Shares are shown above. Diluted earnings per share for Class B Common Shares under the two-class method are $0.04 and $0.09 for the three months ended July 31, 2018 and 2017, respectively. See Note D to the Condensed Consolidated Financial Statements.