Segments and Geographic Information - Operation by Delivery Location (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Segment Reporting Information [Line Items]
Revenues	$ 411,166	$ 402,925
Americas [Member]
Segment Reporting Information [Line Items]
Revenues	332,926	324,777
Americas [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues	332,926	324,777
Americas [Member] | Operating Segments [Member] | United States [Member]
Segment Reporting Information [Line Items]
Revenues	157,666	162,032
Americas [Member] | Operating Segments [Member] | The Philippines [Member]
Segment Reporting Information [Line Items]
Revenues	64,439	56,078
Americas [Member] | Operating Segments [Member] | Costa Rica [Member]
Segment Reporting Information [Line Items]
Revenues	34,881	30,717
Americas [Member] | Operating Segments [Member] | Canada [Member]
Segment Reporting Information [Line Items]
Revenues	25,241	25,564
Americas [Member] | Operating Segments [Member] | El Salvador [Member]
Segment Reporting Information [Line Items]
Revenues	18,720	20,476
Americas [Member] | Operating Segments [Member] | Other [Member]
Segment Reporting Information [Line Items]
Revenues	31,979	29,910
EMEA [Member]
Segment Reporting Information [Line Items]
Revenues	78,233	78,128
EMEA [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues	78,233	78,128
EMEA [Member] | Operating Segments [Member] | Other [Member]
Segment Reporting Information [Line Items]
Revenues	53,582	54,264
EMEA [Member] | Operating Segments [Member] | Germany [Member]
Segment Reporting Information [Line Items]
Revenues	24,651	23,864
Other Segment [Member]
Segment Reporting Information [Line Items]
Revenues	$ 7	$ 20