Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Cash Flows From Operating Activities
Net Income	$ 180,606	$ 88,554
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities:
Net (Gains) Losses on Investments, Marketable Securities and Contingent Consideration	239	3,565
Equity Method Investments	1,863	4,118
Equity-Based and Other Deferred Compensation	163,094	177,812
Impairment of Goodwill and Equity Method Investments	21,507	0
Depreciation, Amortization and Accretion	18,453	19,033
Bad Debt Expense	2,547	1,966
Deferred Taxes	(1,849)	(2,509)
Decrease (Increase) in Operating Assets:
Marketable Securities	707	680
Financial Instruments Owned and Pledged as Collateral at Fair Value	(1,526)	20,621
Securities Purchased Under Agreements to Resell	2,910	(11,584)
Accounts Receivable	23,423	23,414
Receivable from Employees and Related Parties	(2,102)	1,700
Other Assets	9,391	(12,991)
(Decrease) Increase in Operating Liabilities:
Accrued Compensation and Benefits	(52,481)	(49,915)
Accounts Payable and Accrued Expenses	(96)	(9,140)
Securities Sold Under Agreements to Repurchase	(1,405)	(9,070)
Payables to Employees and Related Parties	471	(2,639)
Taxes Payable	(18,471)	10,641
Other Liabilities	(21,624)	(3,855)
Net Cash Provided by Operating Activities	325,657	250,401
Cash Flows From Investing Activities
Investments Purchased	(857)	(1,529)
Distributions of Private Equity Investments	1,140	107
Marketable Securities:
Proceeds from Sales and Maturities	38,436	29,482
Purchases	(22,347)	(52,851)
Purchase of Certificates of Deposit	(63,417)	0
Cash Paid for Acquisitions and Deconsolidation of Cash, net of Cash Acquired	0	(2,877)
(Increase) Decrease in Restricted Cash	0	(5,385)
Purchase of Furniture, Equipment and Leasehold Improvements	(25,142)	(8,511)
Net Cash Provided by (Used in) Investing Activities	(72,187)	(41,564)
Cash Flows From Financing Activities
Issuance of Noncontrolling Interests	110	885
Distributions to Noncontrolling Interests	(26,315)	(25,519)
Cash Paid for Deferred and Contingent Consideration	0	(5,050)
Short-Term Borrowing	30,000	50,000
Repayment of Short-Term Borrowing	(30,000)	(50,000)
Repayment of Subordinated Borrowings	(9,751)	(6,000)
Payment of Notes Payable - Mizuho	0	(120,000)
Issuance of Notes Payable	0	170,000
Debt Issuance Costs	0	(2,084)
Purchase of Treasury Stock and Noncontrolling Interests	(301,001)	(168,260)
Dividends - Class A Stockholders	(40,723)	(37,693)
Net Cash Provided by (Used in) Financing Activities	(377,680)	(193,721)
Effect of Exchange Rate Changes on Cash	5,541	(17,851)
Net Increase (Decrease) in Cash and Cash Equivalents	(118,669)	(2,735)
Cash and Cash Equivalents-Beginning of Period	558,524	448,764
Cash and Cash Equivalents-End of Period	439,855	446,029
SUPPLEMENTAL CASH FLOW DISCLOSURE
Payments for Interest	16,745	11,553
Payments for Income Taxes	88,865	75,213
Accrued Dividends	7,054	5,781
Settlement of Contingent Consideration	$ 10,780	$ 0