Organization and Summary of Significant Accounting Policies - Additional Information (Detail)	3 Months Ended								12 Months Ended
	Apr. 30, 2018 USD ($) $ / shares	Jan. 31, 2018 $ / shares	Oct. 31, 2017 $ / shares	Jul. 31, 2017 $ / shares	Apr. 30, 2017 USD ($) $ / shares	Jan. 31, 2017 $ / shares	Oct. 31, 2016 $ / shares	Jul. 31, 2016 $ / shares	Apr. 30, 2018 USD ($) $ / shares	Apr. 30, 2017 USD ($) $ / shares	Apr. 30, 2016 USD ($) $ / shares	Feb. 17, 2016 / $	Feb. 16, 2016 / $
Organization And Summary Of Significant Accounting Policies [Line Items]
Investments in affiliated companies maximum	50.00%								50.00%
Dividends received from unconsolidated subsidiary									$ 240,000	$ 564,000	$ 2,373,000
Deferred revenue	$ 120,100,000				$ 95,800,000				120,100,000	95,800,000
Impairment of long-lived assets									0	0	0
Impairment of goodwill									0
Impairment of intangible assets									0	0
Performance related bonus expenses									$ 220,400,000	179,600,000	186,500,000
Percentage that Actuarial gain or loss must exceed the greater of PBO or Market Value Plan Assets									10.00%
Foreign currency losses/(gains), after tax									$ 2,200,000	$ (200,000)	8,700,000
Foreign currency exchange rate, translation | / $												10.0	6.3
Venezuelan foreign currency loss											$ 13,720,000
Diluted (loss) earnings per share | $ / shares	$ 0.73	$ 0.48	$ 0.64	$ 0.51	$ 0.47	$ 0.42	$ 0.52	$ 0.06	$ 2.35	$ 1.47	$ 0.58
Increase to cash provided operations									$ 219,125,000	$ 106,141,000	$ 68,989,000
Decrease in cash provided by financing activities									(77,258,000)	64,365,000	$ 113,544,000
CSV of COLI Contracts
Organization And Summary Of Significant Accounting Policies [Line Items]
Gross CSV	$ 186,800,000				$ 180,300,000				186,800,000	180,300,000
Outstanding policy loans	66,700,000				67,200,000				66,700,000	67,200,000
Receivable on insolvency of insurance companies	$ 120,100,000				$ 61,300,000				$ 120,100,000	61,300,000
Devaluation Of Venezuelan Bolivar
Organization And Summary Of Significant Accounting Policies [Line Items]
Diluted (loss) earnings per share | $ / shares											$ (0.26)
Free-Floating Exchange Rate
Organization And Summary Of Significant Accounting Policies [Line Items]
Foreign currency exchange rate, translation | / $												200
Rate used to calculate the impact of devaluation
Organization And Summary Of Significant Accounting Policies [Line Items]
Foreign currency exchange rate, translation | / $												260
Accounting Standards Update 2016-09
Organization And Summary Of Significant Accounting Policies [Line Items]
Increase to cash provided operations										100,000	$ 4,900,000
Decrease in cash provided by financing activities										$ (100,000)	$ (4,900,000)
Minimum
Organization And Summary Of Significant Accounting Policies [Line Items]
Intangible assets estimated useful lives									1 year
Amortization of long-term retention awards									4 years
Minimum | Executive Capital Accumulation Plan
Organization And Summary Of Significant Accounting Policies [Line Items]
Deferred compensation arrangement vesting period									4 years
Minimum | Software and Software Development Costs
Organization And Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful life									3 years
Minimum | Other Capitalized Property Plant and Equipment
Organization And Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful life									3 years
Maximum
Organization And Summary Of Significant Accounting Policies [Line Items]
Intangible assets estimated useful lives									24 years
Amortization of long-term retention awards									5 years
Maximum | Executive Capital Accumulation Plan
Organization And Summary Of Significant Accounting Policies [Line Items]
Deferred compensation arrangement vesting period									5 years
Maximum | Software and Software Development Costs
Organization And Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful life									7 years
Maximum | Other Capitalized Property Plant and Equipment
Organization And Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful life									10 years