Revenues - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue
Revenue	$ 328,501	$ 305,520	$ 647,525	$ 605,551
Time-and-materials
Disaggregation of Revenue
Revenue	199,365	184,170	389,280	363,396
Fixed-price
Disaggregation of Revenue
Revenue	129,136	121,350	258,245	242,155
Application outsourcing
Disaggregation of Revenue
Revenue	181,576	161,890	363,539	322,599
Consulting
Disaggregation of Revenue
Revenue	146,925	143,630	283,986	282,952
Banking financial services insurance
Disaggregation of Revenue
Revenue	193,336	192,071	383,308	380,809
Communications and Technology
Disaggregation of Revenue
Revenue	108,406	85,341	212,907	168,368
Media & Information and Other
Disaggregation of Revenue
Revenue	26,759	28,108	51,310	56,374
North America
Disaggregation of Revenue
Revenue	242,296	218,303	472,776	427,932
Europe
Disaggregation of Revenue
Revenue	57,024	60,393	120,104	127,129
Rest Of World
Disaggregation of Revenue
Revenue	$ 29,181	$ 26,824	$ 54,645	$ 50,490