Segments - Summary of Geographic Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 6,798,327	$ 5,645,142	$ 19,195,819	$ 16,915,694
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	3,943,714	3,162,235	10,856,277	9,632,592
United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	841,241	736,927	2,451,222	2,188,822
All other countries
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 2,013,372	$ 1,745,980	$ 5,888,320	$ 5,094,280