Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Cash Flows From Operating Activities
Net Income	$ 94,647	$ 7,678
Adjustments to Reconcile Net Income to Net Cash Provided by (Used in) Operating Activities:
Net (Gains) Losses on Investments, Marketable Securities and Contingent Consideration	(1,000)	(1,203)
Equity Method Investments	(582)	4,731
Equity-Based and Other Deferred Compensation	28,683	66,870
Depreciation, Amortization and Accretion	5,860	6,382
Bad Debt Expense	351	0
Deferred Taxes	(1,362)	178
Decrease (Increase) in Operating Assets:
Marketable Securities	147	163
Financial Instruments Owned and Pledged as Collateral at Fair Value	(13,175)	8,319
Securities Purchased Under Agreements to Resell	12,284	(111)
Accounts Receivable	30,415	29,229
Receivable from Employees and Related Parties	(3,017)	857
Other Assets	5,111	(7,228)
(Decrease) Increase in Operating Liabilities:
Accrued Compensation and Benefits	(207,556)	(212,762)
Accounts Payable and Accrued Expenses	(2,696)	(11,764)
Securities Sold Under Agreements to Repurchase	883	(8,261)
Payables to Employees and Related Parties	9,095	3,700
Taxes Payable	(18,673)	(8,355)
Other Liabilities	(20,674)	9,052
Net Cash Provided by (Used in) Operating Activities	(81,259)	(112,525)
Cash Flows From Investing Activities
Investments Purchased	(1)	(84)
Distributions of Private Equity Investments	378	3
Marketable Securities:
Proceeds from Sales and Maturities	12,145	5,572
Purchases	(7,583)	(8,906)
Purchase of Furniture, Equipment and Leasehold Improvements	(6,417)	(2,265)
Net Cash Provided by (Used in) Investing Activities	(1,478)	(5,680)
Cash Flows From Financing Activities
Issuance of Noncontrolling Interests	60	0
Distributions to Noncontrolling Interests	(8,601)	(8,585)
Short-Term Borrowing	30,000	50,000
Repayment of Short-Term Borrowing	(30,000)	0
Repayment of Subordinated Borrowings	(6,000)	0
Payment of Notes Payable - Mizuho	0	(120,000)
Issuance of Notes Payable	0	170,000
Debt Issuance Costs	0	(103)
Purchase of Treasury Stock and Noncontrolling Interests	(93,454)	(115,253)
Dividends - Class A Stockholders	(16,035)	(12,328)
Net Cash Provided by (Used in) Financing Activities	(124,030)	(36,269)
Effect of Exchange Rate Changes on Cash	(497)	(2,767)
Net Increase (Decrease) in Cash and Cash Equivalents	(207,264)	(157,241)
Cash and Cash Equivalents-Beginning of Period	558,524	448,764
Cash and Cash Equivalents-End of Period	351,260	291,523
SUPPLEMENTAL CASH FLOW DISCLOSURE
Payments for Interest	6,809	2,240
Payments for Income Taxes	44,580	19,386
Accrued Dividends	2,374	1,940
Debt Issuance Costs Accrued	0	1,981
Settlement of Contingent Consideration	$ 10,780	$ 0