Segments and Geographic Information - Operation by Delivery Location (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Revenue	$ 448,885	$ 416,833	$ 906,771	$ 827,999
Americas [Member]
Segment Reporting Information [Line Items]
Revenue	356,427	339,272	720,146	672,198
Americas [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue	356,427	339,272	720,146	672,198
Americas [Member] | Operating Segments [Member] | United States [Member]
Segment Reporting Information [Line Items]
Revenue	157,174	164,773	327,178	322,437
Americas [Member] | Operating Segments [Member] | Philippines [Member]
Segment Reporting Information [Line Items]
Revenue	70,076	62,567	138,070	127,006
Americas [Member] | Operating Segments [Member] | Costa Rica [Member]
Segment Reporting Information [Line Items]
Revenue	36,722	39,250	74,248	74,131
Americas [Member] | Operating Segments [Member] | Canada [Member]
Segment Reporting Information [Line Items]
Revenue	29,392	22,955	57,379	48,196
Americas [Member] | Operating Segments [Member] | El Salvador [Member]
Segment Reporting Information [Line Items]
Revenue	19,368	16,902	37,364	35,622
Americas [Member] | Operating Segments [Member] | Other [Member]
Segment Reporting Information [Line Items]
Revenue	43,695	32,825	85,907	64,806
EMEA [Member]
Segment Reporting Information [Line Items]
Revenue	92,455	77,561	186,622	155,794
EMEA [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue	92,455	77,561	186,622	155,794
EMEA [Member] | Operating Segments [Member] | Other [Member]
Segment Reporting Information [Line Items]
Revenue	65,203	53,445	130,347	107,027
EMEA [Member] | Operating Segments [Member] | Germany [Member]
Segment Reporting Information [Line Items]
Revenue	27,252	$ 24,116	56,275	48,767
Other Segment [Member]
Segment Reporting Information [Line Items]
Revenue	$ 3		$ 3	$ 7