Consolidated Statements of Financial Condition (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Accumulated depreciation and amortization on fixed assets	$ 68,397	$ 65,991
Accumulated amortization on intangible assets	$ 50,742	$ 40,864
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	19,526,398	19,526,533
Common stock, shares outstanding (in shares)	13,783,930	13,717,315
Common stock held in treasury, shares (in shares)	5,742,468	5,809,218