Condensed Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH WITHIN THE CONDENSED CONSOLIDATED STATEMENTS OF FINANCIAL CONDITION:
Cash and cash equivalents	$ 962,280	$ 1,483,836
Deposits with banks and short-term investments	862,865	935,431
Cash deposited with clearing organizations and other segregated cash	38,643	35,539
TOTAL CASH AND CASH EQUIVALENTS AND RESTRICTED CASH	$ 1,863,788	$ 2,454,806	$ 1,497,638	$ 1,607,483