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		9 Months Ended
		Jan. 31, 2019	Jan. 31, 2018	Jan. 31, 2019	Jan. 31, 2018
Revenues
Revenues		$ 27,003	$ 30,117	$ 82,435	$ 83,340
Cost of revenues:
Cost of revenues		12,964	13,071	39,977	37,063
Gross margin		14,039	17,046	42,458	46,277
Research and development		2,811	3,099	9,818	8,250
Sales and marketing		4,699	5,385	15,183	15,055
General and administrative		4,302	4,263	12,903	11,418
Amortization of acquisition-related intangibles		97	95	291	486
Total operating expenses		11,909	12,842	38,195	35,209
Operating income		2,130	4,204	4,263	11,068
Other income:
Interest income		523	403	1,551	1,120
Other, net		4	1,171	(461)	1,729
Income tax expense		2,657	5,778	5,353	13,917
Income tax expense		356	198	424	3,132
Net earnings		$ 2,301	$ 5,580	$ 4,929	$ 10,785
Earnings per common share (a):
Basic earnings per common share (in usd per share)	[1]	$ 0.07	$ 0.18	$ 0.16	$ 0.36
Diluted earnings per common share (in usd per share)	[1]	$ 0.07	$ 0.18	$ 0.16	$ 0.36
Balances under Prior GAAP
Revenues
Revenues		$ 27,404		$ 82,891
Cost of revenues:
Cost of revenues		12,964		39,977
Gross margin		14,440		42,914
Research and development		2,811		9,818
Sales and marketing		4,740		15,317
General and administrative		4,302		12,903
Amortization of acquisition-related intangibles		97		291
Total operating expenses		11,950		38,329
Operating income		2,490		4,585
Other income:
Interest income		523		1,551
Other, net		4		(461)
Income tax expense		3,017		5,675
Income tax expense		405		468
Net earnings		$ 2,612		$ 5,207
Earnings per common share (a):
Basic earnings per common share (in usd per share)		$ 0.08		$ 0.17
Diluted earnings per common share (in usd per share)		$ 0.08		$ 0.17
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Revenues
Revenues		$ 401		$ 456
Cost of revenues:
Cost of revenues		0		0
Gross margin		401		456
Research and development		0		0
Sales and marketing		41		134
General and administrative		0		0
Amortization of acquisition-related intangibles		0		0
Total operating expenses		41		134
Operating income		360		322
Other income:
Interest income		0		0
Other, net		0		0
Income tax expense		360		322
Income tax expense		49		44
Net earnings		$ 311		$ 278
Earnings per common share (a):
Basic earnings per common share (in usd per share)		$ 0.01		$ 0.01
Diluted earnings per common share (in usd per share)		$ 0.01		$ 0.01
License
Revenues
Revenues		$ 1,718	$ 5,955	$ 5,432	$ 12,420
Cost of revenues:
Cost of revenues		1,831	1,727	5,305	4,692
License | Balances under Prior GAAP
Revenues
Revenues		2,086		5,745
Cost of revenues:
Cost of revenues		1,831		5,305
License | Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Revenues
Revenues		368		313
Cost of revenues:
Cost of revenues		0		0
Subscription Fees
Revenues
Revenues		3,687	2,584	10,196	6,244
Cost of revenues:
Cost of revenues		1,389	1,028	3,746	2,779
Subscription Fees | Balances under Prior GAAP
Revenues
Revenues		3,689		10,202
Cost of revenues:
Cost of revenues		1,389		3,746
Subscription Fees | Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Revenues
Revenues		2		6
Cost of revenues:
Cost of revenues		0		0
Professional Services and Other
Revenues
Revenues		10,176	10,342	32,240	31,773
Cost of revenues:
Cost of revenues		7,714	7,912	24,484	22,673
Professional Services and Other | Balances under Prior GAAP
Revenues
Revenues		10,207		32,377
Cost of revenues:
Cost of revenues		7,714		24,484
Professional Services and Other | Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Revenues
Revenues		31		137
Cost of revenues:
Cost of revenues		0		0
Maintenance
Revenues
Revenues		11,422	11,236	34,567	32,903
Cost of revenues:
Cost of revenues		2,030	$ 2,404	6,442	$ 6,919
Maintenance | Balances under Prior GAAP
Revenues
Revenues		11,422		34,567
Cost of revenues:
Cost of revenues		2,030		6,442
Maintenance | Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Revenues
Revenues		0		0
Cost of revenues:
Cost of revenues		$ 0		$ 0

[1] (a)Basic per share amounts are the same for Class A and Class B shares. Diluted per share amounts for Class A shares are shown above. Diluted earnings per share for Class B shares under the two-class method are $0.07 and $0.18 for the three months ended January 31, 2019 and 2018, and $0.16 and $0.36 for the nine months ended January 31, 2019 and 2018, respectively. See Note D to the Condensed Consolidated Financial Statements.