Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH WITHIN THE CONSOLIDATED STATEMENTS OF FINANCIAL CONDITION:
Cash and cash equivalents	$ 1,231,593	$ 1,246,537	$ 1,483,836
Deposits with banks and short-term investments	1,180,686	1,006,969	935,431
Cash deposited with clearing organizations and other segregated cash	43,280	38,379	35,539
TOTAL CASH AND CASH EQUIVALENTS AND RESTRICTED CASH	2,455,559	2,291,885	2,454,806
Cash paid during the year for:
Interest	70,400	50,812	49,601
Income taxes, net of refunds	$ 89,448	$ 101,671	$ 48,738