Segments and Geographic Information - Operation by Delivery Location (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Revenue	$ 1,614,762	$ 1,625,687	$ 1,586,008
Americas [Member]
Segment Reporting Information [Line Items]
Revenue	1,296,660	1,330,638	1,325,643
Americas [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue	1,296,660	1,330,638	1,325,643
Americas [Member] | Operating Segments [Member] | United States [Member]
Segment Reporting Information [Line Items]
Revenue	614,493	668,580	644,870
Americas [Member] | Operating Segments [Member] | The Philippines [Member]
Segment Reporting Information [Line Items]
Revenue	250,888	231,966	241,211
Americas [Member] | Operating Segments [Member] | Costa Rica [Member]
Segment Reporting Information [Line Items]
Revenue	127,078	127,963	132,542
Americas [Member] | Operating Segments [Member] | Canada [Member]
Segment Reporting Information [Line Items]
Revenue	99,037	102,353	112,367
Americas [Member] | Operating Segments [Member] | El Salvador [Member]
Segment Reporting Information [Line Items]
Revenue	81,195	81,156	75,800
Americas [Member] | Operating Segments [Member] | Other [Member]
Segment Reporting Information [Line Items]
Revenue	123,969	118,620	118,853
EMEA [Member]
Segment Reporting Information [Line Items]
Revenue	318,013	294,954	260,283
EMEA [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue	318,013	294,954	260,283
EMEA [Member] | Operating Segments [Member] | Other [Member]
Segment Reporting Information [Line Items]
Revenue	223,847	203,251	178,649
EMEA [Member] | Operating Segments [Member] | Germany [Member]
Segment Reporting Information [Line Items]
Revenue	94,166	91,703	81,634
Other Segment [Member]
Segment Reporting Information [Line Items]
Revenue	$ 89	$ 95	$ 82