Segment Information - Operating Revenues by Geographic Area (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenues from External Customers and Long-Lived Assets [Line Items]
Operating revenues	$ 549,842	$ 517,099	$ 498,180	$ 478,423	$ 443,661	$ 425,333	$ 409,616	$ 416,780	$ 2,043,544	$ 1,695,390	$ 1,557,796
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Operating revenues									836,880	723,962	698,105
Other [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Operating revenues									85,744	71,408	65,997
Total Americas [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Operating revenues									922,624	795,370	764,102
United Kingdom [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Operating revenues									344,976	262,188	234,926
Other [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Operating revenues									454,239	364,547	325,221
Europe, the Middle East and Africa ("EMEA") [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Operating revenues									799,215	626,735	560,147
Japan [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Operating revenues									91,419	80,591	71,629
Other [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Operating revenues									230,286	192,694	161,918
Total Asia & Australia [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Operating revenues									$ 321,705	$ 273,285	$ 233,547