Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	Voting Common Stock [Member]	Non-Voting Common Stock [Member]	Common Stock [Member] Voting Common Stock [Member]	Common Stock [Member] Non-Voting Common Stock [Member]	Additional Paid-In Capital [Member]	Additional Paid-In Capital [Member] Voting Common Stock [Member]	Additional Paid-In Capital [Member] Non-Voting Common Stock [Member]	Notes Receivable From Stock Option Exercises [Member]	Notes Receivable From Stock Option Exercises [Member] Non-Voting Common Stock [Member]	Accumulated Other Comprehensive Loss [Member]	Retained Earnings [Member]	Retained Earnings [Member] Non-Voting Common Stock [Member]	Non-Redeemable Non-Controlling Interests [Member]	Total Permanent Equity [Member]	Total Permanent Equity [Member] Voting Common Stock [Member]	Total Permanent Equity [Member] Non-Voting Common Stock [Member]	Redeemable Non-Controlling Interests [Member]
Beginning balance at Oct. 31, 2018				$ 2	$ 455	$ 17,514			$ (8,057)		$ (53,181)	$ 1,150,698		$ 1,000	$ 1,108,431			$ 335,097
Net income	$ 92,260											86,801		417	87,218			5,042
Other comprehensive income (loss), net of tax	962										962				962
Dividends declared												(40,386)			(40,386)
Issuance of Non-Voting Common Stock:
On exercise of stock options					1			$ 2,980		$ (199)							$ 2,782
Under employee stock purchase plans								1,593									1,593
Under employee stock purchase incentive plan								472									472
Under restricted stock plan, net of forfeitures					6												6
Stock-based compensation						22,659									22,659
Tax benefit (expense) of non-controlling interest repurchases						992									992
Repurchase of Common Stock					(12)		$ 0	(45,288)					$ (69,733)			$ 0	(115,033)
Principal repayments on notes receivable from stock option exercises									381						381
Net subscriptions (redemptions/distributions) of non-controlling interest holders														(439)	(439)			41,221
Net consolidations (deconsolidations) of sponsored investment funds																		(51,701)
Reclass to temporary equity														28	28			(28)
Purchase of non-controlling interests																		(3,964)
Changes in redemption value of non-controlling interests redeemable at fair value						(922)									(922)			922
Ending balance at Jan. 31, 2019				2	450	0			(7,875)		(55,933)	1,131,094		1,006	1,068,744			326,589
Cumulative effect adjustment upon adoption of new accounting standard (ASU 2016-09)											(3,714)
Cumulative effect adjustment upon adoption of new accounting standard (ASU 2016-09) | Accounting Standards Update 2016-01 [Member]											(3,714)	3,714
Beginning balance, (shares) at Oct. 31, 2019		422,935	113,143,567
Beginning balance at Oct. 31, 2019	1,184,119			2	442	0			(8,447)		(58,317)	1,250,439		0	1,184,119			285,915
Net income	112,835											103,985		207	104,192			8,643
Other comprehensive income (loss), net of tax	(384)										(384)				(384)
Dividends declared												(43,048)			(43,048)
Issuance of Common Stock							$ 581									$ 581
Issuance of Non-Voting Common Stock:
On exercise of stock options					4			31,735		$ (122)							31,617
Under employee stock purchase plans								1,657									1,657
Under employee stock purchase incentive plan					0			2,695									2,695
Under restricted stock plan, net of forfeitures					6												6
Stock-based compensation						29,520									29,520
Tax benefit (expense) of non-controlling interest repurchases						(14)									(14)
Repurchase of Common Stock					(6)			$ (65,870)					$ (745)				$ (66,621)
Principal repayments on notes receivable from stock option exercises									1,215						1,215
Net subscriptions (redemptions/distributions) of non-controlling interest holders														(207)	(207)			41,225
Net consolidations (deconsolidations) of sponsored investment funds																		0
Reclass to temporary equity														0	0			0
Purchase of non-controlling interests																		0
Changes in redemption value of non-controlling interests redeemable at fair value						$ (304)									(304)			304
Ending balance at Jan. 31, 2020	$ 1,245,024			$ 2	$ 446				$ (7,354)		$ (58,701)	$ 1,310,631		$ 0	$ 1,245,024			$ 336,087
Ending balance, (shares) at Jan. 31, 2020		478,643	114,257,084