Organization and Summary of Significant Accounting Policies - Additional Information (Detail)		3 Months Ended		6 Months Ended		12 Months Ended
	Mar. 31, 2020 USD ($)	Oct. 31, 2020 USD ($)	Oct. 31, 2019 USD ($)	Oct. 31, 2020 USD ($) Segment	Oct. 31, 2019 USD ($)	Apr. 30, 2020 USD ($)
Organization And Summary Of Significant Accounting Policies [Line Items]
Number of business segments | Segment				4
Credit loss for available for sales debt securities		$ 0	$ 0	$ 0	$ 0
Impairment of long-lived assets				0	0	$ 0
Goodwill		621,560,000		621,560,000		613,943,000
Impairment of goodwill	$ 0			0		0
Performance-related bonus expenses		$ 72,100,000	$ 64,400,000	$ 132,000,000.0	$ 117,400,000
ASU 2016-13
Organization And Summary Of Significant Accounting Policies [Line Items]
Change in accounting principle, accounting standards update, adopted		true		true
Change in accounting principle, accounting standards update, adoption date		May 01, 2020		May 01, 2020
Change in accounting principle, accounting standards update, immaterial effect		true		true
ASU 2017-04
Organization And Summary Of Significant Accounting Policies [Line Items]
Change in accounting principle, accounting standards update, adopted		true		true
Change in accounting principle, accounting standards update, adoption date		May 01, 2020		May 01, 2020
Change in accounting principle, accounting standards update, immaterial effect		true		true
ASU 2018-13
Organization And Summary Of Significant Accounting Policies [Line Items]
Change in accounting principle, accounting standards update, adopted		true		true
Change in accounting principle, accounting standards update, adoption date		May 01, 2020		May 01, 2020
Change in accounting principle, accounting standards update, immaterial effect		true		true
ASU 2018-15
Organization And Summary Of Significant Accounting Policies [Line Items]
Change in accounting principle, accounting standards update, adopted		true		true
Change in accounting principle, accounting standards update, adoption date		May 01, 2020		May 01, 2020
Change in accounting principle, accounting standards update, immaterial effect		true		true
ASU 2019-12
Organization And Summary Of Significant Accounting Policies [Line Items]
Change in accounting principle, accounting standards update, adopted		true		true
Change in accounting principle, accounting standards update, adoption date		May 01, 2020		May 01, 2020
Change in accounting principle, accounting standards update, immaterial effect		true		true
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
Consulting | Operating Segments
Organization And Summary Of Significant Accounting Policies [Line Items]
Goodwill						$ 173,000,000.0
Acquired Companies
Organization And Summary Of Significant Accounting Policies [Line Items]
Business acquisitions adjustment, increase in goodwill				$ 2,600,000
Affiliated Entity
Organization And Summary Of Significant Accounting Policies [Line Items]
Investments in affiliated companies maximum		50.00%		50.00%
Mexican Subsidiary
Organization And Summary Of Significant Accounting Policies [Line Items]
Percentage of Noncontrolling interest in subsidiary		51.00%		51.00%