Organization and Summary of Significant Accounting Policies - Additional Information (Detail)	3 Months Ended		9 Months Ended		12 Months Ended
	Jan. 31, 2019 USD ($)	Jan. 31, 2018 USD ($)	Jan. 31, 2019 USD ($) Segment	Jan. 31, 2018 USD ($)	Apr. 30, 2018 USD ($)	May 01, 2018 USD ($)
Organization And Summary Of Significant Accounting Policies [Line Items]
Number of business segments | Segment			3
Impairment of goodwill			$ 0		$ 0
Impairment of intangible assets	$ 0		0		$ 0
Purchase price allocated to indefinite lived trade name intangible assets	106,600,000		106,600,000
Performance-related bonus expenses	59,500,000	$ 56,800,000	202,400,000	$ 155,200,000
Accounting Standards Update 2014-09 | Adjustments Due to ASC 606
Organization And Summary Of Significant Accounting Policies [Line Items]
Increase to retained earnings, net of tax						$ 6,700,000
Accounting Standards Update 2018-02
Organization And Summary Of Significant Accounting Policies [Line Items]
Increase to retained earnings, net of tax	$ 2,200,000		2,200,000
General and Administrative Expenses
Organization And Summary Of Significant Accounting Policies [Line Items]
Impairment of intangible assets			$ 106,600,000
Compensation Expense | Accounting Standards Update 2017-07
Organization And Summary Of Significant Accounting Policies [Line Items]
Reclassification adjustment revised amount		1,200,000		3,600,000
Other Income | Accounting Standards Update 2017-07
Organization And Summary Of Significant Accounting Policies [Line Items]
Reclassification adjustment revised amount		(200,000)		(500,000)
Interest Expense | Accounting Standards Update 2017-07
Organization And Summary Of Significant Accounting Policies [Line Items]
Reclassification adjustment revised amount		$ (1,000,000)		$ (3,100,000)
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
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
Affiliated Entity
Organization And Summary Of Significant Accounting Policies [Line Items]
Investments in affiliated companies maximum	50.00%		50.00%
Mexico Subsidiary
Organization And Summary Of Significant Accounting Policies [Line Items]
Percentage of Noncontrolling interest in subsidiary	51.00%		51.00%