Presentation and Summary of Significant Accounting Policies - Summary of Effect of Adopting Topic 606 on Condensed Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Jul. 31, 2018	May 01, 2018	Apr. 30, 2018	Jul. 31, 2017	Apr. 30, 2017
Current assets:
Cash and cash equivalents	$ 54,855	$ 52,794	$ 52,794	$ 66,227	$ 66,001
Investments	29,992	26,121	26,121
Trade accounts receivable, net
Billed	13,683	18,643	18,643
Unbilled	3,311	3,815	3,375
Prepaid expenses and other current assets	6,433	6,718	6,592
Total current assets	108,274	108,091	107,525
Investments-noncurrent	2,509	8,893	8,893
Property and equipment, net	3,600	3,034	3,034
Capitalized software, net	9,559	9,728	9,728
Goodwill	25,888	25,888	25,888
Other intangibles, net	4,523	5,120	5,120
Other assets	4,055	4,102	2,777
Total assets	158,408	164,856	162,965
Current liabilities:
Accounts payable	2,166	1,974	1,974
Accrued compensation and related costs	2,305	6,310	6,310
Dividends payable	3,400	3,367	3,367
Other current liabilities	925	1,326	1,246
Deferred revenue	29,518	32,705	33,226
Total current liabilities	38,314	45,682	46,123
Deferred income taxes	3,222	3,194	2,615
Long-term deferred revenue		147	147
Other long-term liabilities	1,485	1,496	1,496
Total liabilities	43,021	50,519	50,381
Shareholders' equity:
Additional paid-incapital	134,292	131,258	131,258
Retained earnings	3,105	5,119	3,366
Class A treasury stock	(25,559)	(25,559)	(25,559)
Total shareholders' equity	115,387	114,337	112,584
Commitments and contingencies
Total liabilities and shareholders' equity	158,408	164,856	162,965
Balances under Prior GAAP
Current assets:
Cash and cash equivalents	54,855
Investments	29,992
Trade accounts receivable, net
Billed	13,683
Unbilled	2,872
Prepaid expenses and other current assets	6,265
Total current assets	107,667
Investments-noncurrent	2,509
Property and equipment, net	3,600
Capitalized software, net	9,559
Goodwill	25,888
Other intangibles, net	4,523
Other assets	2,844
Total assets	156,590
Current liabilities:
Accounts payable	2,166
Accrued compensation and related costs	2,305
Dividends payable	3,400
Other current liabilities	845
Deferred revenue	30,526
Total current liabilities	39,242
Deferred income taxes	2,719
Other long-term liabilities	1,485
Total liabilities	43,446
Shareholders' equity:
Additional paid-incapital	134,292
Retained earnings	862
Class A treasury stock	(25,559)
Total shareholders' equity	113,144
Commitments and contingencies
Total liabilities and shareholders' equity	156,590
Class A Common Shares
Shareholders' equity:
Common stock value	3,367	3,314	3,314
Class A Common Shares | Balances under Prior GAAP
Shareholders' equity:
Common stock value	3,367
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	(439)		440
Prepaid expenses and other current assets	(168)		126
Total current assets	(607)		566
Other assets	(1,211)		1,325
Total assets	(1,818)		1,891
Current liabilities:
Other current liabilities	(80)		80
Deferred revenue	1,008		(521)
Total current liabilities	928		(441)
Deferred income taxes	(503)		579
Total liabilities	425		138
Shareholders' equity:
Retained earnings	(2,243)		1,753
Total shareholders' equity	(2,243)		1,753
Commitments and contingencies
Total liabilities and shareholders' equity	$ (1,818)		$ 1,891