Consolidated Statements of Cash Flows $ in Thousands	12 Months Ended
	Oct. 31, 2019 USD ($)	Oct. 31, 2018 USD ($)	Oct. 31, 2017 USD ($)
Cash Flows From Operating Activities:
Net income	$ 432,876	$ 397,905	$ 306,373
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	23,706	25,013	19,132
Unamortized loss on derivative instrument	0	0	(684)
Amortization of deferred sales commissions	22,592	18,394	16,231
Stock-based compensation	90,998	87,047	79,525
Deferred income taxes	4,503	25,246	14,345
Net (gains) losses on investments and derivatives	(8,255)	17,796	1,900
Loss on expiration of Hexavest option	0	6,523	0
Equity in net income of affiliates, net of tax	(9,090)	(11,373)	(10,870)
Dividends received from affiliates	10,927	12,243	11,447
Loss on extinguishment of debt	0	0	5,396
Consolidated CLO entities' operating activities:
Net (gains) losses on bank loan, other investments and note obligations	4,240	(1,999)	0
Amortization of bank loan investments	(1,447)	(248)	0
(Increase) decrease in other assets, net of other liabilities	12,680	(150)	0
Increase in cash due to initial consolidation	19,009	51,278	0
Changes in operating assets and liabilities:
Management fees and other receivables	(1,052)	(36,427)	(14,167)
Short-term debt securities	(24,663)	(59,551)	(126,996)
Investments held by consolidated sponsored funds and separatley managed accounts	(28,492)	(181,797)	(253,748)
Deferred sales commissions	(29,169)	(30,598)	(25,577)
Other assets	(1,459)	(1,960)	(11,250)
Accrued compensation	6,674	26,806	33,489
Accounts payable and accrued expenses	(4,924)	10,287	7,330
Other liabilities	(7,836)	5,286	44,032
Net cash provided by operating activities	511,818	359,721	95,908
Cash Flows From Investing Activities:
Additions to equipment and leasehold improvements	(34,897)	(18,747)	(12,698)
Net cash paid in acquisition	0	0	(63,605)
Proceeds from sale of investments	14,067	24,486	16,502
Purchase of investments	(3,514)	(7,022)	(276)
Proceeds from sale of investments in CLO entity note obligations	0	76,563	0
Purchase of investments in CLO entity note obligations	(54,352)	(147,322)	0
Consolidated CLO entities' investing activities:
Proceeds from sales of bank loans and other investments	501,356	154,871	0
Purchase of bank loans and other investments	(1,098,530)	(407,883)	(31,348)
Net cash used for investing activities	(675,870)	(325,054)	(91,425)
Cash Flows From Financing Activities:
Purchase of additional non-controlling interest	(91,617)	(20,818)	(9,820)
Line of credit issuance costs	(930)	0	0
Debt issuance costs	0	0	(2,761)
Proceeds from issuance of debt	0	0	298,896
Repayment of debt	0	0	(250,000)
Loss on extinguishment of debt	0	0	(5,396)
Principal repayments on notes receivable from stock option exercises	1,183	4,825	4,500
Dividends paid	(159,123)	(144,855)	(125,785)
Net subscriptions received from (redemptions/distributions paid to) non-controlling interest holders	44,508	100,360	188,463
Consolidated CLO entities' financing activities:
Proceeds from line of credit	197,915	245,898	12,598
Repayment of line of credit	(197,915)	(258,496)	0
Issuance of senior and subordinated notes obligations	794,767	1,320,397	0
Principal repayments of senior and subordinated note obligations	(389,000)	(865,624)	0
Net cash provided by (used for) financing activities	(48,356)	184,413	195,430
Effect of currency rate changes on cash and cash equivalents	(322)	(2,868)	2,701
Net increase (decrease) in cash, cash equivalents and restricted cash	(212,730)	216,212	202,614
Cash, cash equivalents and restricted cash, beginning of year	866,075	649,863	447,249
Cash, cash equivalents and restricted cash, end of year	653,345	866,075	649,863
Supplemental Cash and Restricted Cash Flow Information:
Cash paid for interest	22,695	22,660	25,535
Cash paid for interest upon repayment of debt	0	0	1,354
Cash paid for interest by consolidated CLO entities	38,140	10,681	0
Cash paid for income taxes, net of refunds	125,054	135,105	143,948
Supplemental Schedule of Non-Cash Investing and Financing Transactions:
Increase in equipment and leasehold improvements due to non-cash additions	4,341	1,336	863
Exercise of stock options through issuance of notes receivable	1,573	1,770	3,538
Increase (decrease) in non-controlling interests due to net consolidations (deconsolidations) of sponsored investment funds	(67,989)	(25,320)	129,587
Decrease in bank loans and other investments of consolidated CLO entities due to unsettled sales	(24,193)	0	0
Increase in bank loans and other investments of consolidated CLO entities due to unsettled purchases	33,985	149,617	0
Non-controlling interest call option exercises recorded in other liabilities	8,372	14,133	12,379
Initial Consolidation of CLO Entities:
Increase in bank loans and other investments	410,853	814,122	0
Increase in senior loan obligations	391,080	843,089	0
Deconsolidation of CLO Entities:
Decrease in bank loans and other investments	0	(379,676)	0
Decrease in senior and subordinated loan obligations	0	(378,742)	0
Non-Voting Common Stock [Member]
Cash Flows From Financing Activities:
Proceeds from issuance of Non-Voting Common Stock	51,256	76,447	210,934
Repurchase of Common Stock	(299,400)	(273,550)	(126,199)
Supplemental Schedule of Non-Cash Investing and Financing Transactions:
Non-Voting Common Stock repurchases recorded in accounts payable and accrued expenses	13,670	13,136	0
Voting Common Stock [Member]
Cash Flows From Financing Activities:
Repurchase of Common Stock	$ 0	$ (171)	$ 0