Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	Voting Common Stock [Member]	Non-Voting Common Stock [Member]	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]	Accumulated Other Comprehensive Income (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, (shares) at Oct. 31, 2016				113,988,000
Beginning balance at Oct. 31, 2016					$ 2	$ 444	$ 0			$ (12,074)	$ (57,583)	$ 773,000		$ 786	$ 704,575			$ 109,028
Net income	$ 306,373											282,131		4,079	286,210			20,163
Other comprehensive income (loss), net of tax	10,109										10,109				10,109
Dividends declared												(133,896)			(133,896)
Issuance of Non-Voting Common Stock:
On exercise of stock options (shares)						5,599,000
On exercise of stock options						$ 22			$ 207,471	(3,538)							$ 203,955
Under employee stock purchase plans (shares)						95,000
Under employee stock purchase plans									2,976								2,976
Under employee stock purchase incentive plan (shares)						108,000
Under employee stock purchase incentive plan									3,997								3,997
Under restricted stock plan, net of forfeitures (shares)						1,625,000
Under restricted stock plan, net of forfeitures						$ 6											6
Stock-based compensation							79,525								79,525
Tax benefit of stock option exercises and vesting of restricted stock awards							3,165								3,165
Tax benefit (expense) associated with non-controlling interest							8,454								8,454
Repurchase of Common Stock						$ (11)			(126,188)								(126,199)
Repurchase of Common Stock (shares)						(2,894,000)
Principal repayments on notes receivable from stock option exercises										4,500					4,500
Net subscriptions (redemptions/distributions) of non-controlling interest holders														(3,937)	(3,937)			191,822
Net consolidations (deconsolidations) of sponsored investment funds																		(81,382)
Reclass to temporary equity														(64)	(64)			64
Purchase of non-controlling interests																		(19,988)
Changes in redemption value of non-controlling interests redeemable at fair value							(31,116)								(31,116)			31,116
Ending balance at Oct. 31, 2017					2	$ 461	148,284			(11,112)	(47,474)	921,235		864	1,012,260			250,823
Ending balance, (shares) at Oct. 31, 2017				118,521,000
Net income	397,905											381,938		3,049	384,987			12,918
Other comprehensive income (loss), net of tax	(5,707)										(5,707)				(5,707)
Dividends declared												(151,952)			(151,952)
Issuance of Non-Voting Common Stock:
On exercise of stock options (shares)						2,526,000
On exercise of stock options						$ 11			70,156	(1,770)							68,397
Under employee stock purchase plans (shares)						76,000
Under employee stock purchase plans									3,168								3,168
Under employee stock purchase incentive plan (shares)						104,000
Under employee stock purchase incentive plan									4,877								4,877
Under restricted stock plan, net of forfeitures (shares)						1,308,000
Under restricted stock plan, net of forfeitures						$ 5									5
Stock-based compensation							87,047								87,047
Tax benefit (expense) associated with non-controlling interest							5,649								5,649
Repurchase of Common Stock						(22)		$ (171)	(286,664)							$ (171)	(286,686)
Repurchase of Common Stock (shares)		(20,000)	(5,564,000)
Principal repayments on notes receivable from stock option exercises										4,825					4,825
Net subscriptions (redemptions/distributions) of non-controlling interest holders														(2,947)	(2,947)			103,775
Net consolidations (deconsolidations) of sponsored investment funds																		(25,320)
Reclass to temporary equity														34	34			(34)
Purchase of non-controlling interests																		(22,572)
Changes in redemption value of non-controlling interests redeemable at fair value							(15,507)								(15,507)			15,507
Ending balance at Oct. 31, 2018	1,108,431				2	455	17,514			(8,057)	(53,181)	1,150,698		1,000	1,108,431			335,097
Ending balance, (shares) at Oct. 31, 2018		422,935	116,527,845	116,951,000
Cumulative effect adjustment upon adoption of new accounting standard (ASU 2016-09)							675					(523)			152
Net income	432,876											400,035		1,812	401,847			31,029
Other comprehensive income (loss), net of tax	$ (1,422)										(1,422)				(1,422)
Dividends declared												(162,592)			(162,592)
Issuance of Non-Voting Common Stock:
On exercise of stock options (shares)	1,570,000			1,570,000
On exercise of stock options						6	45,023			(1,573)					43,456
Under employee stock purchase plans (shares)				82,000
Under employee stock purchase plans							3,197								3,197
Under employee stock purchase incentive plan (shares)				126,000
Under employee stock purchase incentive plan							4,594								4,594
Under restricted stock plan, net of forfeitures (shares)				2,247,000
Under restricted stock plan, net of forfeitures						9									9
Stock-based compensation							90,998								90,998
Tax benefit (expense) associated with non-controlling interest							21,944								21,944
Repurchase of Common Stock						$ (28)			$ (158,490)				$ (141,416)				$ (299,934)
Repurchase of Common Stock (shares)		0				(7,409,000)
Principal repayments on notes receivable from stock option exercises										1,183					1,183
Net subscriptions (redemptions/distributions) of non-controlling interest holders														(2,190)	(2,190)			48,233
Net consolidations (deconsolidations) of sponsored investment funds																		(67,989)
Reclass to temporary equity														(622)	(622)			622
Purchase of non-controlling interests																		(85,857)
Changes in redemption value of non-controlling interests redeemable at fair value							(24,780)								(24,780)			24,780
Ending balance at Oct. 31, 2019	$ 1,184,119				$ 2	$ 442	$ 0			$ (8,447)	(58,317)	1,250,439		$ 0	$ 1,184,119			$ 285,915
Ending balance, (shares) at Oct. 31, 2019		422,935	113,143,567	113,567,000
Cumulative effect adjustment upon adoption of new accounting standard (ASU 2016-09)											$ (3,714)	$ 3,714