Condensed Consolidated Statements of Cash Flows - USD ($)	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash Flows From Operating Activities
Net Income	$ 106,108,000	$ 175,457,000
Adjustments to Reconcile Net Income to Net Cash Provided by (Used In) Operating Activities:
Net (Gains) Losses on Investments, Investment Securities and Contingent Consideration	11,780,000	(9,985,000)
Equity Method Investments	3,309,000	3,402,000
Equity-Based and Other Deferred Compensation	176,968,000	192,286,000
Noncash Lease Expense	18,284,000	11,316,000
Depreciation, Amortization and Accretion	15,989,000	16,898,000
Bad Debt Expense	5,331,000	1,750,000
Deferred Taxes	2,112,000	(12,427,000)
Decrease (Increase) in Operating Assets:
Investment Securities	2,601,000	(514,000)
Financial Instruments Owned and Pledged as Collateral at Fair Value	(6,486,000)	120,000
Securities Purchased Under Agreements to Resell	6,334,000	(210,000)
Accounts Receivable	(25,778,000)	(9,800,000)
Receivable from Employees and Related Parties	(612,000)	4,133,000
Other Assets	33,968,000	(87,498,000)
(Decrease) Increase in Operating Liabilities:
Accrued Compensation and Benefits	(241,190,000)	(411,865,000)
Accounts Payable and Accrued Expenses	62,000	(176,000)
Securities Sold Under Agreements to Repurchase	149,000	68,000
Payables to Employees and Related Parties	5,529,000	13,757,000
Taxes Payable	380,000	(29,702,000)
Other Liabilities	3,932,000	7,911,000
Net Cash Provided (Used In) by Operating Activities	118,770,000	(135,079,000)
Cash Flows From Investing Activities
Investments Purchased	0	(2,819,000)
Distributions of Private Equity Investments	234,000	364,000
Investment Securities:
Proceeds from Sales and Maturities of Investment Securities and Futures Contracts Activity	543,251,000	263,490,000
Purchases of Investment Securities and Futures Contracts Activity	(244,470,000)	(266,486,000)
Maturity of Certificates of Deposit	214,266,000	100,000,000
Purchase of Furniture, Equipment and Leasehold Improvements	(29,665,000)	(26,282,000)
Net Cash Provided by Investing Activities	483,616,000	68,267,000
Cash Flows From Financing Activities
Issuance of Noncontrolling Interests	540,000	0
Distributions to Noncontrolling Interests	(14,009,000)	(31,696,000)
Short-Term Borrowings	0	30,000,000
Repayment of Short-Term Borrowings	0	(30,000,000)
Purchase of Treasury Stock and Noncontrolling Interests	(143,412,000)	(265,043,000)
Dividends	(57,529,000)	(50,797,000)
Net Cash Provided by (Used in) Financing Activities	(214,410,000)	(347,536,000)
Effect of Exchange Rate Changes on Cash	(6,842,000)	(1,133,000)
Net Increase (Decrease) in Cash, Cash Equivalents and Restricted Cash	381,134,000	(415,481,000)
Cash, Cash Equivalents and Restricted Cash-Beginning of Period	643,886,000	800,096,000
Cash, Cash Equivalents and Restricted Cash-End of Period	1,025,020,000	384,615,000
SUPPLEMENTAL CASH FLOW DISCLOSURE
Payments for Interest	12,856,000	8,400,000
Payments for Income Taxes	23,646,000	79,357,000
Accrued Dividends	6,918,000	7,125,000
Noncash Purchase of Noncontrolling Interest	$ 851,000	$ 2,701,000