Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	Voting Common Stock [Member]	Non-Voting Common Stock [Member]	Additional Paid-In Capital [Member]	Notes Receivable From Stock Option Exercises [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]	Non-Redeemable Non-Controlling Interests [Member]	Total Permanent Equity [Member]	Redeemable Non-Controlling Interests [Member]
Beginning balance, at Oct. 31, 2016		$ 2	$ 444	$ 0	$ (12,074)	$ (57,583)	$ 773,000	$ 786	$ 704,575	$ 109,028
Net income	$ 64,341						60,711	892	61,603	2,738
Other comprehensive income (loss), net of tax	6,128					6,128			6,128
Dividends declared							(32,260)		(32,260)
Issuance of Non-Voting Common Stock:
On exercise of stock options			3	26,215	(330)				25,888
Under employee stock purchase plans				1,516					1,516
Under employee stock purchase incentive plan				324					324
Under restricted stock plan, net of forfeitures			6						6
Stock-based compensation				20,178					20,178
Tax benefit of stock option exercises and vesting of restricted stock awards				4,858					4,858
Repurchase of Non-Voting Common Stock	53,601		(5)	(53,596)					(53,601)
Principal repayments on notes receivable from stock option exercises					2,263				2,263
Net subscriptions (redemptions/distributions) of non-controlling interest holders								(874)	(874)	44,152
Reclass to temporary equity								(64)	(64)	64
Purchase of non-controlling interests										(6,941)
Changes in redemption value of non-controlling interests redeemable at fair value				(377)					(377)	377
Ending balance, at Jan. 31, 2017		2	448	2,777	(10,141)	(51,455)	801,451	740	743,822	149,418
Issuance of Non-Voting Common Stock:
Tax benefit of non-controlling interest repurchases				3,659					3,659
Beginning balance, at Oct. 31, 2017	1,012,260	2	461	148,284	(11,112)	(47,474)	921,235	864	1,012,260	250,823
Net income	88,511						78,056	742	78,798	9,713
Other comprehensive income (loss), net of tax	12,780					12,780			12,780
Dividends declared							(37,276)		(37,276)
Issuance of Non-Voting Common Stock:
On exercise of stock options			6	42,690	(393)				42,303
Under employee stock purchase plans				1,549					1,549
Under employee stock purchase incentive plan				427					427
Under restricted stock plan, net of forfeitures			5						5
Stock-based compensation				23,729					23,729
Repurchase of Non-Voting Common Stock	36,343		(3)	(36,340)					(36,343)
Principal repayments on notes receivable from stock option exercises					987				987
Net subscriptions (redemptions/distributions) of non-controlling interest holders								(739)	(739)	52,244
Net consolidations (deconsolidations) of sponsored investment funds and CLO entities										(488)
Reclass to temporary equity								34	34	(34)
Purchase of non-controlling interests										(8,439)
Changes in redemption value of non-controlling interests redeemable at fair value				(630)					(630)	630
Ending balance, at Jan. 31, 2018	$ 1,100,154	$ 2	$ 469	182,502	$ (10,518)	$ (34,694)	961,492	$ 901	1,100,154	$ 304,449
Cumulative effect adjustment upon adoption of new accounting standard (ASU 2016-09)				675			$ (523)		152
Issuance of Non-Voting Common Stock:
Tax benefit of non-controlling interest repurchases				$ 2,118					$ 2,118