Presentation and Summary of Significant Accounting Policies - Summary of Effect of Adopting Topic 606 on Condensed Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Oct. 31, 2018	May 01, 2018	Apr. 30, 2018	Oct. 31, 2017	Apr. 30, 2017
Current assets:
Cash and cash equivalents	$ 50,933	$ 52,794	$ 52,794	$ 61,242	$ 66,001
Investments	29,816	26,121	26,121
Trade accounts receivable, net
Billed	17,427	18,643	18,643
Unbilled	3,104	3,815	3,375
Prepaid expenses and other current assets	6,568	6,718	6,592
Total current assets	107,848	108,091	107,525
Investments-noncurrent	1,925	8,893	8,893
Property and equipment, net	3,609	3,034	3,034
Capitalized software, net	9,618	9,728	9,728
Goodwill	25,888	25,888	25,888
Other intangibles, net	3,926	5,120	5,120
Other assets	3,776	4,102	2,777
Total assets	156,590	164,856	162,965
Current liabilities:
Accounts payable	1,475	1,974	1,974
Accrued compensation and related costs	2,829	6,310	6,310
Dividends payable	3,405	3,367	3,367
Other current liabilities	1,362	1,326	1,246
Deferred revenue	29,395	32,705	33,226
Total current liabilities	38,466	45,682	46,123
Deferred income taxes	2,929	3,194	2,615
Long-term deferred revenue		147	147
Other long-term liabilities	1,107	1,496	1,496
Total liabilities	42,502	50,519	50,381
Shareholders' equity:
Additional paid-incapital	135,150	131,258	131,258
Retained earnings	943	5,119	3,366
Class A treasury stock	(25,559)	(25,559)	(25,559)
Total shareholders' equity	114,088	114,337	112,584
Commitments and contingencies
Total liabilities and shareholders' equity	156,590	164,856	162,965
Balances under Prior GAAP
Current assets:
Cash and cash equivalents	50,933
Investments	29,816
Trade accounts receivable, net
Billed	17,427
Unbilled	2,715
Prepaid expenses and other current assets	6,317
Total current assets	107,208
Investments-noncurrent	1,925
Property and equipment, net	3,609
Capitalized software, net	9,618
Goodwill	25,888
Other intangibles, net	3,926
Other assets	2,585
Total assets	154,759
Current liabilities:
Accounts payable	1,475
Accrued compensation and related costs	2,829
Dividends payable	3,405
Other current liabilities	1,282
Deferred revenue	30,014
Total current liabilities	39,005
Deferred income taxes	2,345
Other long-term liabilities	1,107
Total liabilities	42,457
Shareholders' equity:
Additional paid-incapital	135,150
Retained earnings	(843)
Class A treasury stock	(25,559)
Total shareholders' equity	112,302
Commitments and contingencies
Total liabilities and shareholders' equity	154,759
Class A Common Shares
Shareholders' equity:
Common stock value	3,372	3,314	3,314
Class A Common Shares | Balances under Prior GAAP
Shareholders' equity:
Common stock value	3,372
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
Trade accounts receivable, net
Unbilled	(389)		440
Prepaid expenses and other current assets	(251)		126
Total current assets	(640)		566
Other assets	(1,191)		1,325
Total assets	(1,831)		1,891
Current liabilities:
Other current liabilities	(80)		80
Deferred revenue	619		(521)
Total current liabilities	539		(441)
Deferred income taxes	(584)		579
Total liabilities	(45)		138
Shareholders' equity:
Retained earnings	(1,786)		1,753
Total shareholders' equity	(1,786)		1,753
Commitments and contingencies
Total liabilities and shareholders' equity	$ (1,831)		$ 1,891