Business Segments - Revenue and Long-Lived Assets by Geographic Location (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Revenues from External Customers and Long-Lived Assets [Line Items]
Service revenues	$ 6,392,517	$ 7,238,142	$ 6,461,444
Property and equipment, net	108,809	109,687
Domestic
Revenues from External Customers and Long-Lived Assets [Line Items]
Service revenues	4,957,163	5,712,330	5,006,525
Property and equipment, net	87,664	90,388
Foreign
Revenues from External Customers and Long-Lived Assets [Line Items]
Service revenues	1,435,354	1,525,812	$ 1,454,919
Property and equipment, net	$ 21,145	$ 19,299