Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash Flows From Operating Activities
Net Income	$ 109,736	$ 94,647
Adjustments to Reconcile Net Income to Net Cash Provided by (Used in) Operating Activities:
Net (Gains) Losses on Investments, Marketable Securities and Contingent Consideration	(210)	(1,000)
Equity Method Investments	(384)	(582)
Equity-Based and Other Deferred Compensation	67,626	28,683
Depreciation, Amortization and Accretion	6,712	5,860
Bad Debt Expense	1,025	351
Deferred Taxes	(438)	(1,362)
Decrease (Increase) in Operating Assets:
Marketable Securities	(101)	147
Financial Instruments Owned and Pledged as Collateral at Fair Value	(972)	(13,175)
Securities Purchased Under Agreements to Resell	799	12,284
Accounts Receivable	(37,303)	30,415
Receivable from Employees and Related Parties	(3,708)	(3,017)
Other Assets	614	5,164
(Decrease) Increase in Operating Liabilities:
Accrued Compensation and Benefits	(177,635)	(207,556)
Accounts Payable and Accrued Expenses	2,468	(2,696)
Securities Sold Under Agreements to Repurchase	169	883
Payables to Employees and Related Parties	13,640	9,095
Taxes Payable	(11,988)	(18,673)
Other Liabilities	(10,735)	(20,674)
Net Cash Provided by (Used in) Operating Activities	(40,685)	(81,206)
Cash Flows From Investing Activities
Investments Purchased	0	(1)
Distributions of Private Equity Investments	270	378
Marketable Securities:
Proceeds from Sales and Maturities	23,347	12,145
Purchases	(54,840)	(7,583)
Maturity of Certificates of Deposit	63,527	0
Purchase of Furniture, Equipment and Leasehold Improvements	(4,151)	(6,417)
Net Cash Provided by (Used in) Investing Activities	28,153	(1,478)
Cash Flows From Financing Activities
Issuance of Noncontrolling Interests	60	60
Distributions to Noncontrolling Interests	(13,193)	(8,601)
Short-Term Borrowing	30,000	30,000
Repayment of Short-Term Borrowing	(30,000)	(30,000)
Repayment of Subordinated Borrowings	(6,700)	(6,000)
Purchase of Treasury Stock and Noncontrolling Interests	(155,597)	(93,454)
Dividends - Class A Stockholders	(16,538)	(16,035)
Net Cash Provided by (Used in) Financing Activities	(191,968)	(124,030)
Effect of Exchange Rate Changes on Cash	3,473	(497)
Net Increase (Decrease) in Cash, Cash Equivalents and Restricted Cash	(201,027)	(207,211)
Cash, Cash Equivalents and Restricted Cash-Beginning of Period	617,385	575,637
Cash, Cash Equivalents and Restricted Cash-End of Period	416,358	368,426
SUPPLEMENTAL CASH FLOW DISCLOSURE
Payments for Interest	6,868	6,809
Payments for Income Taxes	19,833	44,580
Accrued Dividends	2,631	2,374
Purchase of Noncontrolling Interest	9,164	0
Settlement of Contingent Consideration	$ 0	$ 10,780