Condensed Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH WITHIN THE CONDENSED CONSOLIDATED STATEMENTS OF FINANCIAL CONDITION:
Cash and cash equivalents	$ 959,001	$ 1,246,537
Deposits with banks and short-term investments	1,289,288	1,006,969
Cash deposited with clearing organizations and other segregated cash	40,280	38,379
TOTAL CASH AND CASH EQUIVALENTS AND RESTRICTED CASH	$ 2,288,569	$ 2,291,885	$ 2,186,252	$ 2,454,806