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Deferred Compensation and Retirement Plans - Additional Information (Detail) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Jan. 31, 2019 | Jan. 31, 2018 | Jan. 31, 2019 | Jan. 31, 2018 | Apr. 30, 2018
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Increase in market value of the underlying COLI investments |  |  | $ 4,547 | $ 6,020 |
Recognized investment income (expense) | $ 2,200 | $ 7,200 | 1,330 | 14,022 |
Executive Capital Accumulation Plan |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Gain (loss) on deferred compensation plan | 2,200 | 7,200 | $ 2,000 | 14,400 |
Minimum |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Option to receive employee benefits by quarterly installments periods |  |  | 1 year |  |
Minimum | Executive Capital Accumulation Plan |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Deferred compensation arrangement vesting period |  |  | 4 years |  |
Maximum |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Option to receive employee benefits by quarterly installments periods |  |  | 15 years |  |
Maximum | Executive Capital Accumulation Plan |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Deferred compensation arrangement vesting period |  |  | 5 years |  |
CSV of COLI Contracts |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Gross CSV | 218,800 |  | $ 218,800 |  | $ 186,800
Outstanding policy loans | 94,200 |  | 94,200 |  | $ 66,700
Increase in market value of the underlying COLI investments | $ 1,500 | $ 1,800 | $ 4,500 | $ 6,000 |

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- Definition Minimum period the individual is required to perform services to be fully vested under the deferred compensation arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 710 -SubTopic 10 -Section 55 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=6409961&loc=d3e20487-108367 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition The change in cash surrender or contract value during the period which adjusted the amount of premiums paid in determining the expense or income recognized under the contract for the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 325 -SubTopic 30 -Section 35 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6384439&loc=d3e42048-111605 + Details
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