Fair Value Disclosures (Schedule of Assets and Liabilities Measured on Recurring Basis at Fair Value) (Details) - USD ($) $ in Thousands	May 31, 2020	Nov. 30, 2019
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	$ 17,629,541	$ 16,308,807
Counterparty and cash collateral netting, assets	(1,528,340)	(1,433,197)
Securities purchased under agreements to resell		25,000
Securities received as collateral, at fair value	9,909	9,500
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	9,646,023	10,532,460
Counterparty and Cash Collateral Netting, liabilities	(1,682,883)	(1,632,178)
Short-term borrowings	15,671	20,981
Long-term debt	1,245,486	1,215,285
Obligation to return securities received as collateral, at fair value	9,909	9,500
Level 1
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	6,483,545	5,941,623
Securities purchased under agreements to resell		0
Securities received as collateral, at fair value	9,909	9,500
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	5,046,211	5,971,928
Short-term borrowings	0	0
Long-term debt	0	0
Obligation to return securities received as collateral, at fair value	9,909	9,500
Level 2
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	12,056,349	11,245,763
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:	6,179,273	6,086,328
Short-term borrowings	15,671	20,981
Long-term debt	748,446	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	617,987	554,618
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:	103,422	106,382
Short-term borrowings	0	0
Long-term debt	497,040	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	912,936	586,934
Corporate equity securities
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	2,724,291	2,783,993
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	1,778,244	2,767,526
Obligation to return securities received as collateral, at fair value	0	0
Corporate equity securities | Level 1
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	2,586,764	2,507,164
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	1,772,771	2,755,601
Corporate equity securities | Level 2
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	61,387	218,403
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	1,283	7,438
Corporate equity securities | Level 3
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	76,140	58,426
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	4,190	4,487
Corporate debt securities
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	3,004,979	2,479,735
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	1,491,252	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	2,979,801	2,472,245
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	1,491,089	1,471,142
Corporate debt securities | Level 3
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	25,178	7,490
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	163	340
Collateralized debt obligations and collateralized loan obligations
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	100,299	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	68,748	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	31,551	28,788
U.S. government and federal agency securities
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	1,880,603	2,260,242
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	2,140,501	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	1,808,192	2,101,624
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	2,140,501	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	72,411	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	462,420	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	462,420	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	3,395,410	2,735,853
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	2,010,721	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	2,088,074	1,330,026
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	1,132,662	1,363,475
Sovereign obligations | Level 2
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	1,307,336	1,405,827
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	878,059	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	1,710,718	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	1,688,379	1,069,066
Residential mortgage-backed securities | Level 3
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	22,339	17,740
Commercial mortgage-backed securities
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	359,622	430,170
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	140	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	355,161	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	4,461	6,110
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	140	35
Other asset-backed securities
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	378,220	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	292,158	303,847
Other asset-backed securities | Level 3
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	86,062	42,563
Loans and other receivables
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	2,692,523	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	2,571,394	2,460,551
Loans and other receivables | Level 3
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	121,129	114,080
Derivatives, assets
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	640,593	418,408
Derivatives, assets | Level 1
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	515	2,809
Derivatives, assets | Level 2
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	2,125,294	1,833,907
Derivatives, assets | Level 3
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	43,124	14,889
Investments at fair value
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	226,098	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	71,860	32,688
Investments at fair value | Level 3
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	154,238	205,412
FXCM term loan
Assets:
Financial instruments owned, at fair value, excluding investments at fair value based on NAV	53,765	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	53,765	59,120
Loans
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	1,807,265	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:	1,796,591	1,600,228
Loans | Level 3
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	10,674	9,463
Derivatives, liabilities
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	417,900	527,205
Derivatives, liabilities | Level 1
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	277	871
Derivatives, liabilities | Level 2
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	2,012,251	2,066,455
Derivatives, liabilities | Level 3
Liabilities:
Financial instruments sold, not yet purchased, at fair value:	$ 88,255	$ 92,057