Fair Value Disclosures - Financial Assets and Liabilities Accounted for at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Aug. 31, 2020	Nov. 30, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Alternative investment	$ 920,327	$ 570,310
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	16,635,393	15,793,064
Counterparty and Cash Collateral Netting	(1,611,815)	(1,432,806)
Securities purchased under agreements to resell		25,000
Securities received as collateral	4,413	9,500
Financial instruments sold, not yet purchased:
Total financial instruments sold, not yet purchased	10,994,445	10,532,460
Counterparty and Cash Collateral Netting	(1,799,681)	(1,631,787)
Short-term borrowings	21,829	20,981
Other secured financings	3,402
Obligation to return securities received as collateral, at fair value	4,413	9,500
Long-term debt	1,522,105	1,215,285
Corporate equity securities
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	2,587,896	2,601,820
Financial instruments sold, not yet purchased:
Total financial instruments sold, not yet purchased	2,312,291	2,767,526
Corporate debt securities
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	2,743,850	2,479,703
Financial instruments sold, not yet purchased:
Total financial instruments sold, not yet purchased	1,448,706	1,471,482
Collateralized debt obligations and collateralized loan obligations
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	96,223	144,306
U.S. government and federal agency securities
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	3,256,508	2,260,242
Financial instruments sold, not yet purchased:
Total financial instruments sold, not yet purchased	2,722,907	1,851,981
Municipal securities
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	358,292	742,326
Sovereign obligations
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	2,563,856	2,735,853
Financial instruments sold, not yet purchased:
Total financial instruments sold, not yet purchased	2,548,575	2,304,540
Residential mortgage-backed securities
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	1,003,483	1,086,806
Commercial mortgage-backed securities
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	1,096,069	430,170
Financial instruments sold, not yet purchased:
Total financial instruments sold, not yet purchased	35	35
Other asset-backed securities
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	112,071	346,410
Loans and other receivables
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	2,217,871	2,459,451
Derivative assets
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	504,237	397,551
Investments at fair value
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	95,037	108,426
Loans
Financial instruments sold, not yet purchased:
Total financial instruments sold, not yet purchased	1,478,707	1,609,691
Derivative liabilities
Financial instruments sold, not yet purchased:
Total financial instruments sold, not yet purchased	483,224	527,205
Fair value based on net asset value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Alternative investment	920,300	570,300
Level 1
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	7,300,701	5,759,575
Securities purchased under agreements to resell		0
Securities received as collateral	4,413	9,500
Financial instruments sold, not yet purchased:
Total financial instruments sold, not yet purchased	6,471,728	5,971,928
Short-term borrowings	0	0
Other secured financings	0
Obligation to return securities received as collateral, at fair value	4,413	9,500
Long-term debt	0	0
Level 1 | Corporate equity securities
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	2,446,810	2,325,116
Financial instruments sold, not yet purchased:
Total financial instruments sold, not yet purchased	2,295,391	2,755,601
Level 1 | Corporate debt securities
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	0	0
Financial instruments sold, not yet purchased:
Total financial instruments sold, not yet purchased	0	0
Level 1 | Collateralized debt obligations and collateralized loan obligations
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	0	0
Level 1 | U.S. government and federal agency securities
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	3,164,472	2,101,624
Financial instruments sold, not yet purchased:
Total financial instruments sold, not yet purchased	2,722,907	1,851,981
Level 1 | Municipal securities
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	0	0
Level 1 | Sovereign obligations
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	1,686,522	1,330,026
Financial instruments sold, not yet purchased:
Total financial instruments sold, not yet purchased	1,452,399	1,363,475
Level 1 | Residential mortgage-backed securities
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	0	0
Level 1 | Commercial mortgage-backed securities
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	0	0
Financial instruments sold, not yet purchased:
Total financial instruments sold, not yet purchased	0	0
Level 1 | Other asset-backed securities
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	0	0
Level 1 | Loans and other receivables
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	0	0
Level 1 | Derivative assets
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	2,897	2,809
Level 1 | Investments at fair value
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	0	0
Level 1 | Loans
Financial instruments sold, not yet purchased:
Total financial instruments sold, not yet purchased	0	0
Level 1 | Derivative liabilities
Financial instruments sold, not yet purchased:
Total financial instruments sold, not yet purchased	1,031	871
Level 2
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	10,513,645	11,159,143
Securities purchased under agreements to resell		0
Securities received as collateral	0	0
Financial instruments sold, not yet purchased:
Total financial instruments sold, not yet purchased	6,196,634	6,085,937
Short-term borrowings	21,829	20,981
Other secured financings	0
Obligation to return securities received as collateral, at fair value	0	0
Long-term debt	891,845	735,216
Level 2 | Corporate equity securities
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	63,256	218,403
Financial instruments sold, not yet purchased:
Total financial instruments sold, not yet purchased	12,533	7,438
Level 2 | Corporate debt securities
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	2,720,581	2,472,213
Financial instruments sold, not yet purchased:
Total financial instruments sold, not yet purchased	1,448,558	1,471,142
Level 2 | Collateralized debt obligations and collateralized loan obligations
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	68,287	124,225
Level 2 | U.S. government and federal agency securities
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	92,036	158,618
Financial instruments sold, not yet purchased:
Total financial instruments sold, not yet purchased	0	0
Level 2 | Municipal securities
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	358,292	742,326
Level 2 | Sovereign obligations
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	877,334	1,405,827
Financial instruments sold, not yet purchased:
Total financial instruments sold, not yet purchased	1,096,176	941,065
Level 2 | Residential mortgage-backed securities
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	975,166	1,069,066
Level 2 | Commercial mortgage-backed securities
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	1,091,406	424,060
Financial instruments sold, not yet purchased:
Total financial instruments sold, not yet purchased	0	0
Level 2 | Other asset-backed securities
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	48,734	303,847
Level 2 | Loans and other receivables
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	2,112,437	2,395,211
Level 2 | Derivative assets
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	2,060,960	1,812,659
Level 2 | Investments at fair value
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	45,156	32,688
Level 2 | Loans
Financial instruments sold, not yet purchased:
Total financial instruments sold, not yet purchased	1,432,113	1,600,228
Level 2 | Derivative liabilities
Financial instruments sold, not yet purchased:
Total financial instruments sold, not yet purchased	2,207,254	2,066,064
Level 3
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	432,862	307,152
Securities purchased under agreements to resell		25,000
Securities received as collateral	0	0
Financial instruments sold, not yet purchased:
Total financial instruments sold, not yet purchased	125,764	106,382
Short-term borrowings	0	0
Other secured financings	3,402
Obligation to return securities received as collateral, at fair value	0	0
Long-term debt	630,260	480,069
Level 3 | Corporate equity securities
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	77,830	58,301
Financial instruments sold, not yet purchased:
Total financial instruments sold, not yet purchased	4,367	4,487
Level 3 | Corporate debt securities
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	23,269	7,490
Financial instruments sold, not yet purchased:
Total financial instruments sold, not yet purchased	148	340
Level 3 | Collateralized debt obligations and collateralized loan obligations
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	27,936	20,081
Level 3 | U.S. government and federal agency securities
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	0	0
Financial instruments sold, not yet purchased:
Total financial instruments sold, not yet purchased	0	0
Level 3 | Municipal securities
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	0	0
Level 3 | Sovereign obligations
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	0	0
Financial instruments sold, not yet purchased:
Total financial instruments sold, not yet purchased	0	0
Level 3 | Residential mortgage-backed securities
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	28,317	17,740
Level 3 | Commercial mortgage-backed securities
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	4,663	6,110
Financial instruments sold, not yet purchased:
Total financial instruments sold, not yet purchased	35	35
Level 3 | Other asset-backed securities
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	63,337	42,563
Level 3 | Loans and other receivables
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	105,434	64,240
Level 3 | Derivative assets
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	52,195	14,889
Level 3 | Investments at fair value
Financial instruments owned:
Total financial instruments owned, excluding Investments at fair value based on NAV	49,881	75,738
Level 3 | Loans
Financial instruments sold, not yet purchased:
Total financial instruments sold, not yet purchased	46,594	9,463
Level 3 | Derivative liabilities
Financial instruments sold, not yet purchased:
Total financial instruments sold, not yet purchased	$ 74,620	$ 92,057