Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH WITHIN THE CONSOLIDATED STATEMENTS OF FINANCIAL CONDITION:
Cash and cash equivalents	$ 1,246,537	$ 1,483,836	$ 1,158,785
Deposits with banks and short-term investments	1,006,969	935,431	419,668
Cash deposited with clearing organizations and other segregated cash	38,379	35,539	29,030
TOTAL CASH AND CASH EQUIVALENTS AND RESTRICTED CASH	2,291,885	2,454,806	1,607,483
Cash paid during the year for:
Interest	50,812	49,601	46,262
Income taxes, net of refunds	$ 101,671	$ 48,738	$ 72,420