Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Oct. 31, 2019	Oct. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	$ 181,907	$ 139,332
Investments held at cost	20,904	20,874
Investments in non-consolidated CLO entities	1,417	2,895
Investments in equity method investees	139,510	141,506
Derivative instruments, assets	2,075	6,347
Assets of consolidated CLO entities: Bank loans and other investments	1,704,270	874,304
Total financial assets	2,948,991	2,098,610
Derivative instruments, liabilities	3,314	4,446
Liabilities of consolidated CLO entities: Senior and subordinated note	1,617,095	873,008
Total financial liabilities	1,620,409	877,454
Debt Securities: Short-term [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investment securities, trading	297,845	273,320
Debt Securities: Held by consolidated sponsored funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investment securities, trading	330,966	404,973
Debt Securities: Held in separately managed accounts [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investment securities, trading	55,426	65,060
Equity Securities: Held by consolidated sponsored funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investment securities	183,106	135,609
Equity Securities: Held in separately managed accounts [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investment securities	21,236	24,061
Equity Securities: Non-consolidated sponsored funds and other [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investment securities	10,329	10,329
Other Assets Not Held at Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	0	0
Investments held at cost	20,904	20,874
Investments in non-consolidated CLO entities	1,417	2,895
Investments in equity method investees	139,510	141,506
Derivative instruments, assets	0	0
Assets of consolidated CLO entities: Bank loans and other investments	0	0
Total financial assets	161,831	165,275
Derivative instruments, liabilities	0	0
Liabilities of consolidated CLO entities: Senior and subordinated note	0	0
Total financial liabilities	0	0
Other Assets Not Held at Fair Value [Member] | Debt Securities: Short-term [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investment securities, trading	0	0
Other Assets Not Held at Fair Value [Member] | Debt Securities: Held by consolidated sponsored funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investment securities, trading	0	0
Other Assets Not Held at Fair Value [Member] | Debt Securities: Held in separately managed accounts [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investment securities, trading	0	0
Other Assets Not Held at Fair Value [Member] | Equity Securities: Held by consolidated sponsored funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investment securities	0	0
Other Assets Not Held at Fair Value [Member] | Equity Securities: Held in separately managed accounts [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investment securities	0	0
Other Assets Not Held at Fair Value [Member] | Equity Securities: Non-consolidated sponsored funds and other [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investment securities	0	0
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	24,640	23,262
Investments held at cost	0	0
Investments in non-consolidated CLO entities	0	0
Investments in equity method investees	0	0
Derivative instruments, assets	0	0
Assets of consolidated CLO entities: Bank loans and other investments	0	0
Total financial assets	126,268	140,662
Derivative instruments, liabilities	0	0
Liabilities of consolidated CLO entities: Senior and subordinated note	0	0
Total financial liabilities	0	0
Level 1 [Member] | Debt Securities: Short-term [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investment securities, trading	0	0
Level 1 [Member] | Debt Securities: Held by consolidated sponsored funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investment securities, trading	0	12,834
Level 1 [Member] | Debt Securities: Held in separately managed accounts [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investment securities, trading	0	521
Level 1 [Member] | Equity Securities: Held by consolidated sponsored funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investment securities	70,646	73,291
Level 1 [Member] | Equity Securities: Held in separately managed accounts [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investment securities	21,168	23,642
Level 1 [Member] | Equity Securities: Non-consolidated sponsored funds and other [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investment securities	9,814	7,112
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	157,267	116,070
Investments held at cost	0	0
Investments in non-consolidated CLO entities	0	0
Investments in equity method investees	0	0
Derivative instruments, assets	2,075	6,347
Assets of consolidated CLO entities: Bank loans and other investments	1,702,769	872,757
Total financial assets	2,659,391	1,791,126
Derivative instruments, liabilities	3,314	4,446
Liabilities of consolidated CLO entities: Senior and subordinated note	1,617,095	873,008
Total financial liabilities	1,620,409	877,454
Level 2 [Member] | Debt Securities: Short-term [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investment securities, trading	297,845	273,320
Level 2 [Member] | Debt Securities: Held by consolidated sponsored funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investment securities, trading	297,845	392,139
Level 2 [Member] | Debt Securities: Held in separately managed accounts [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investment securities, trading	55,426	64,539
Level 2 [Member] | Equity Securities: Held by consolidated sponsored funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investment securities	112,460	62,318
Level 2 [Member] | Equity Securities: Held in separately managed accounts [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investment securities	68	419
Level 2 [Member] | Equity Securities: Non-consolidated sponsored funds and other [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investment securities	515	3,217
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	0	0
Investments held at cost	0	0
Investments in non-consolidated CLO entities	0	0
Investments in equity method investees	0	0
Derivative instruments, assets	0	0
Assets of consolidated CLO entities: Bank loans and other investments	1,501	1,547
Total financial assets	1,501	1,547
Derivative instruments, liabilities	0	0
Liabilities of consolidated CLO entities: Senior and subordinated note	0	0
Total financial liabilities	0	0
Level 3 [Member] | Debt Securities: Short-term [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investment securities, trading	0	0
Level 3 [Member] | Debt Securities: Held by consolidated sponsored funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investment securities, trading	0	0
Level 3 [Member] | Debt Securities: Held in separately managed accounts [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investment securities, trading	0	0
Level 3 [Member] | Equity Securities: Held by consolidated sponsored funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investment securities	0	0
Level 3 [Member] | Equity Securities: Held in separately managed accounts [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investment securities	0	0
Level 3 [Member] | Equity Securities: Non-consolidated sponsored funds and other [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investment securities	$ 0	$ 0