Presentation and Summary of Significant Accounting Policies - Summary of Effect of Adopting Topic 606 on Condensed Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Jan. 31, 2019	May 01, 2018	Apr. 30, 2018	Jan. 31, 2018	Apr. 30, 2017
Current assets:
Cash and cash equivalents	$ 55,058	$ 52,794	$ 52,794	$ 54,912	$ 66,001
Investments	28,106	26,121	26,121
Trade accounts receivable, net
Billed	20,298	18,643	18,643
Unbilled	2,992	3,815	3,375
Prepaid expenses and other current assets	6,184	6,718	6,592
Total current assets	112,638	108,091	107,525
Investments—noncurrent	998	8,893	8,893
Property and equipment, net	3,562	3,034	3,034
Capitalized software, net	10,497	9,728	9,728
Goodwill	25,888	25,888	25,888
Other intangibles, net	3,328	5,120	5,120
Other assets	3,910	4,102	2,777
Total assets	160,821	164,856	162,965
Current liabilities:
Accounts payable	1,789	1,974	1,974
Accrued compensation and related costs	2,909	6,310	6,310
Dividends payable	3,417	3,367	3,367
Other current liabilities	1,279	1,326	1,246
Deferred revenue	32,947	32,705	33,226
Total current liabilities	42,341	45,682	46,123
Deferred income taxes	3,027	3,194	2,615
Long-term deferred revenue	0	147	147
Other long-term liabilities	1,097	1,496	1,496
Total liabilities	46,465	50,519	50,381
Shareholders’ equity:
Additional paid-incapital	136,522	131,258	131,258
Retained (deficit) earnings	(172)	5,119	3,366
Class A treasury stock	(25,559)	(25,559)	(25,559)
Total shareholders’ equity	114,356	114,337	112,584
Total liabilities and shareholders’ equity	160,821	164,856	162,965
Balances under Prior GAAP
Current assets:
Cash and cash equivalents	55,058
Investments	28,106
Trade accounts receivable, net
Billed	20,298
Unbilled	2,653
Prepaid expenses and other current assets	6,004
Total current assets	112,119
Investments—noncurrent	998
Property and equipment, net	3,562
Capitalized software, net	10,497
Goodwill	25,888
Other intangibles, net	3,328
Other assets	2,607
Total assets	158,999
Current liabilities:
Accounts payable	1,789
Accrued compensation and related costs	2,909
Dividends payable	3,417
Other current liabilities	1,199
Deferred revenue	33,214
Total current liabilities	42,528
Deferred income taxes	2,492
Long-term deferred revenue	0
Other long-term liabilities	1,097
Total liabilities	46,117
Shareholders’ equity:
Additional paid-incapital	136,522
Retained (deficit) earnings	(1,646)
Class A treasury stock	(25,559)
Total shareholders’ equity	112,882
Total liabilities and shareholders’ equity	158,999
Class A Common Shares
Shareholders’ equity:
Common stock value	3,383	3,314	3,314
Class A Common Shares | Balances under Prior GAAP
Shareholders’ equity:
Common stock value	3,383
Class B Common Shares
Shareholders’ equity:
Common stock value	182	$ 205	205
Class B Common Shares | Balances under Prior GAAP
Shareholders’ equity:
Common stock value	182
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Current assets:
Cash and cash equivalents	0		0
Investments	0		0
Trade accounts receivable, net
Billed	0		0
Unbilled	(339)		440
Prepaid expenses and other current assets	(180)		126
Total current assets	(519)		566
Investments—noncurrent	0		0
Property and equipment, net	0		0
Capitalized software, net	0		0
Goodwill	0		0
Other intangibles, net	0		0
Other assets	(1,303)		1,325
Total assets	(1,822)		1,891
Current liabilities:
Accounts payable	0		0
Accrued compensation and related costs	0		0
Dividends payable	0		0
Other current liabilities	(80)		80
Deferred revenue	267		(521)
Total current liabilities	187		(441)
Deferred income taxes	(535)		579
Long-term deferred revenue	0		0
Other long-term liabilities	0		0
Total liabilities	(348)		138
Shareholders’ equity:
Additional paid-incapital	0		0
Retained (deficit) earnings	(1,474)		1,753
Class A treasury stock	0		0
Total shareholders’ equity	(1,474)		1,753
Total liabilities and shareholders’ equity	(1,822)		1,891
Accounting Standards Update 2014-09 | Class A Common Shares | Difference between Revenue Guidance in Effect before and after Topic 606
Shareholders’ equity:
Common stock value	0		0
Accounting Standards Update 2014-09 | Class B Common Shares | Difference between Revenue Guidance in Effect before and after Topic 606
Shareholders’ equity:
Common stock value	$ 0		$ 0