Fair Value Disclosures (Schedule of Assets and Liabilities Measured on Recurring Basis at Fair Value) (Details) - USD ($) $ in Thousands	Aug. 31, 2020	Nov. 30, 2019
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	$ 17,058,503	$ 16,308,807
Counterparty and cash collateral netting, assets	(1,611,815)	(1,433,197)
Loans to and investments in associated companies	43,092
Securities purchased under agreements to resell		25,000
Securities received as collateral, at fair value	4,413	9,500
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	10,994,556	10,532,460
Counterparty and cash collateral netting, liabilities	(1,799,681)	(1,632,178)
Short-term borrowings	21,829	20,981
Other secured financings	3,402
Long-term debt	1,522,105	1,215,285
Obligation to return securities received as collateral, at fair value	4,413	9,500
Level 1
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	7,448,613	5,941,623
Loans to and investments in associated companies	0
Securities purchased under agreements to resell		0
Securities received as collateral, at fair value	4,413	9,500
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	6,471,728	5,971,928
Short-term borrowings	0	0
Other secured financings	0
Long-term debt	0	0
Obligation to return securities received as collateral, at fair value	4,413	9,500
Level 2
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	10,543,880	11,245,763
Loans to and investments in associated companies	8,404
Securities purchased under agreements to resell		0
Securities received as collateral, at fair value	0	0
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	6,196,745	6,086,328
Short-term borrowings	21,829	20,981
Other secured financings	0
Long-term debt	891,845	735,216
Obligation to return securities received as collateral, at fair value	0	0
Level 3
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	677,825	554,618
Loans to and investments in associated companies	34,688
Securities purchased under agreements to resell		25,000
Securities received as collateral, at fair value	0	0
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	125,764	106,382
Short-term borrowings	0	0
Other secured financings	3,402
Long-term debt	630,260	480,069
Obligation to return securities received as collateral, at fair value	0	0
Fair value measured at NAV
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Alternative investments	928,218	586,934
Corporate equity securities
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	2,735,919	2,783,993
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	2,312,291	2,767,526
Obligation to return securities received as collateral, at fair value	4,413	0
Corporate equity securities | Level 1
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	2,594,722	2,507,164
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	2,295,391	2,755,601
Corporate equity securities | Level 2
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	63,256	218,403
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	12,533	7,438
Corporate equity securities | Level 3
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	77,941	58,426
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	4,367	4,487
Corporate debt securities
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	2,743,913	2,479,735
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	1,448,706	1,471,482
Obligation to return securities received as collateral, at fair value	0	0
Corporate debt securities | Level 1
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	0	0
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	0	0
Corporate debt securities | Level 2
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	2,720,644	2,472,245
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	1,448,558	1,471,142
Corporate debt securities | Level 3
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	23,269	7,490
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	148	340
Collateralized debt obligations and collateralized loan obligations
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	104,409	153,013
Collateralized debt obligations and collateralized loan obligations | Level 1
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	0	0
Collateralized debt obligations and collateralized loan obligations | Level 2
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	68,287	124,225
Collateralized debt obligations and collateralized loan obligations | Level 3
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	36,122	28,788
U.S. government and federal agency securities
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	3,256,508	2,260,242
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	2,722,907	1,851,981
U.S. government and federal agency securities | Level 1
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	3,164,472	2,101,624
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	2,722,907	1,851,981
U.S. government and federal agency securities | Level 2
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	92,036	158,618
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	0	0
U.S. government and federal agency securities | Level 3
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	0	0
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	0	0
Municipal securities
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	358,292	742,326
Liabilities:
Obligation to return securities received as collateral, at fair value	0	0
Municipal securities | Level 1
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	0	0
Municipal securities | Level 2
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	358,292	742,326
Municipal securities | Level 3
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	0	0
Sovereign obligations
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	2,563,856	2,735,853
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	2,548,575	2,304,540
Obligation to return securities received as collateral, at fair value	0	0
Sovereign obligations | Level 1
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	1,686,522	1,330,026
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	1,452,399	1,363,475
Sovereign obligations | Level 2
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	877,334	1,405,827
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	1,096,176	941,065
Sovereign obligations | Level 3
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	0	0
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	0	0
Residential mortgage-backed securities
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	1,003,483	1,086,806
Residential mortgage-backed securities | Level 1
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	0	0
Residential mortgage-backed securities | Level 2
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	975,166	1,069,066
Residential mortgage-backed securities | Level 3
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	28,317	17,740
Commercial mortgage-backed securities
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	1,096,069	430,170
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	35	35
Commercial mortgage-backed securities | Level 1
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	0	0
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	0	0
Commercial mortgage-backed securities | Level 2
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	1,091,406	424,060
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	0	0
Commercial mortgage-backed securities | Level 3
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	4,663	6,110
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	35	35
Other asset-backed securities
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	112,071	346,410
Other asset-backed securities | Level 1
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	0	0
Other asset-backed securities | Level 2
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	48,734	303,847
Other asset-backed securities | Level 3
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	63,337	42,563
Loans and other receivables
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	2,280,103	2,574,631
Liabilities:
Obligation to return securities received as collateral, at fair value	0	0
Loans and other receivables | Level 1
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	0	0
Loans and other receivables | Level 2
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	2,117,162	2,460,551
Loans and other receivables | Level 3
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	162,941	114,080
Derivatives, assets
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	529,684	418,408
Derivatives, assets | Level 1
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	2,897	2,809
Derivatives, assets | Level 2
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	2,086,407	1,833,907
Derivatives, assets | Level 3
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	52,195	14,889
Investments at fair value
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	217,654	238,100
Investments at fair value | Level 1
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	0	0
Investments at fair value | Level 2
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	45,156	32,688
Investments at fair value | Level 3
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	172,498	205,412
FXCM term loan
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	56,542	59,120
FXCM term loan | Level 1
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	0	0
FXCM term loan | Level 2
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	0	0
FXCM term loan | Level 3
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	56,542	59,120
Loans
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	1,478,707	1,609,691
Loans | Level 1
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	0	0
Loans | Level 2
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	1,432,113	1,600,228
Loans | Level 3
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	46,594	9,463
Derivatives, liabilities
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	483,335	527,205
Derivatives, liabilities | Level 1
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	1,031	871
Derivatives, liabilities | Level 2
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	2,207,365	2,066,455
Derivatives, liabilities | Level 3
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	$ 74,620	$ 92,057