Fixed Assets, Net - Components of Fixed Assets, Net (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Property, Plant and Equipment
Fixed assets, gross	$ 343,472	$ 339,838
Accumulated depreciation and amortization	(169,787)	(161,803)
Fixed assets, net	173,685	178,035
Leasehold improvements, furniture and fixtures, and other fixed assets
Property, Plant and Equipment
Fixed assets, gross	246,185	245,262
Software, including software development costs
Property, Plant and Equipment
Fixed assets, gross	59,238	56,883
Computer and communications equipment
Property, Plant and Equipment
Fixed assets, gross	$ 38,049	$ 37,693