Deferred Compensation and Retirement Plans - Additional Information (Detail) $ in Thousands	12 Months Ended
	Apr. 30, 2016 USD ($) Person	Apr. 30, 2015 USD ($) Person	Apr. 30, 2014 USD ($)	Dec. 01, 2015 USD ($)	Apr. 30, 2013 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Recognized investment income	$ (3,333)	$ 8,829	$ 9,498
Increase in market value of the underlying COLI investments	3,984	10,509	8,242
Net CSV	107,296	102,691
Defined benefit pension plan current and non-current	234,059	191,446
Defined benefit pension plan, current	17,946	18,014
Defined benefit pension plan, non-current	$ 216,113	173,432
Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Target allocation range, minimum	50.00%
Target allocation range, maximum	70.00%
Debt Securities
Defined Benefit Plan Disclosure [Line Items]
Target allocation range, minimum	30.00%
Target allocation range, maximum	50.00%
Other Assets
Defined Benefit Plan Disclosure [Line Items]
Target allocation range, minimum	0.00%
Target allocation range, maximum	10.00%
CSV of COLI Contracts
Defined Benefit Plan Disclosure [Line Items]
Gross CSV	$ 175,700	172,300
Outstanding policy loans	68,400	69,600
Total death benefits payable, net of loans	216,700	216,500
Increase in market value of the underlying COLI investments	4,000	10,500	8,200
Pension Plans Defined Benefit, Supplemental Pension Benefits, and Medical And Life Insurance | Legacy Hay Group
Defined Benefit Plan Disclosure [Line Items]
Defined benefit pension plan current and non-current	37,400
Pension Plans Defined Benefit, Supplemental Pension Benefits, and Medical And Life Insurance | Legacy Hay Group | Compensation and Benefits Payable
Defined Benefit Plan Disclosure [Line Items]
Defined benefit pension plan, current	1,100
Pension Plans Defined Benefit, Supplemental Pension Benefits, and Medical And Life Insurance | Legacy Hay Group | Deferred Compensation and Other Retirement Plans
Defined Benefit Plan Disclosure [Line Items]
Defined benefit pension plan, non-current	$ 36,300
Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Participant employment term, maximum years	20 years
Total benefit obligation	$ 5,219	5,262	4,424		$ 4,536
Defined benefit pension plan current and non-current	5,219	5,262
Pension Plans, Defined Benefit | Legacy Hay Group
Defined Benefit Plan Disclosure [Line Items]
Total benefit obligation	35,192			$ 32,795
Defined benefit pension plan current and non-current	10,325
Defined benefit pension plan, non-current	10,325
Deferred Compensation Plan
Defined Benefit Plan Disclosure [Line Items]
Deferred compensation and pension plans in periodic benefit expense cost expected to be recognized	3,100
Total benefit obligation	82,546	83,876	82,153		$ 85,562
Defined benefit pension plan current and non-current	82,546	83,876
Executive Capital Accumulation Plan
Defined Benefit Plan Disclosure [Line Items]
Total benefit obligation	105,676	99,461	89,308
Company's contributions	$ 23,200	19,100	17,200
Deferred compensation arrangement vesting period	4 years
(Loss) gain on deferred compensation plan	$ (1,654)	5,871	$ 8,900
Company's contributions, unamortized portion	33,200	29,700
Defined benefit pension plan current and non-current	105,676	99,461
Defined Contribution Plan
Defined Benefit Plan Disclosure [Line Items]
Company's matching contributions	$ 1,700	1,600
Percentage contribution by the participants to defined contribution plan	50.00%
Company Owned Life Insurance Held In Trust | CSV of COLI Contracts
Defined Benefit Plan Disclosure [Line Items]
Net CSV	$ 72,700
Total death benefits, net of loans held in trust	122,500
Medical And Life Insurance | Legacy Hay Group
Defined Benefit Plan Disclosure [Line Items]
Total benefit obligation	13,006			$ 12,322
Defined benefit pension plan, current	$ 673
Defined benefit plan health care cost trend rate assumed	7.00%
Defined benefit plan ultimate health care cost trend rate	5.00%
Defined benefit plan year that rate reaches ultimate trend rate	2022
Defined benefit plan effect of one percentage point increase on accumulated postretirement benefit obligation	$ 100
Defined benefit plan effect of one percentage point decrease on accumulated postretirement benefit obligation	$ 100
Enhanced Wealth Accumulation Plan
Defined Benefit Plan Disclosure [Line Items]
Participant contribution period towards deferred compensation plans (in years)	8 years
Participant after tax contribution period towards deferred compensation plans (in years)	15 years
Additional deferred units to acquire (in years)	5 years
Senior Executive Incentive Plan
Defined Benefit Plan Disclosure [Line Items]
Participant contribution period towards deferred compensation plans (in years)	4 years
Participant after tax contribution period towards deferred compensation plans (in years)	15 years
International Retirement Plans
Defined Benefit Plan Disclosure [Line Items]
Total benefit obligation	$ 15,678	$ 2,847
Long-term benefit obligation accrued, number of participants | Person	1,450	393
Company's contributions	$ 5,100	$ 500
Defined benefit pension plan current and non-current	15,678	$ 2,847
International Retirement Plans | Legacy Hay Group
Defined Benefit Plan Disclosure [Line Items]
Total benefit obligation	$ 12,400
Long-term benefit obligation accrued, number of participants | Person	741
Company's contributions	$ 1,500