Fixed Assets, Net - Components of Fixed Assets, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment
Fixed assets, gross	$ 339,838	$ 286,718
Accumulated depreciation and amortization	(161,803)	(131,079)
Fixed assets, net	178,035	155,639
Leasehold improvements, furniture and fixtures, and other fixed assets
Property, Plant and Equipment
Fixed assets, gross	245,262	207,020
Software, including software development costs
Property, Plant and Equipment
Fixed assets, gross	56,883	48,112
Computer and communications equipment
Property, Plant and Equipment
Fixed assets, gross	$ 37,693	$ 31,586