Post-retirement Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Post-retirement Benefits
Type of defined benefit plans	us-gaap:PensionPlansDefinedBenefitMember	us-gaap:PensionPlansDefinedBenefitMember	us-gaap:PensionPlansDefinedBenefitMember
Components of net periodic pension expense
Expected return on plan assets	$ (876)	$ (807)	$ (692)
Service costs for benefits earned	2,750	1,914	1,464
Interest cost on projected benefit obligation	985	741	660
Amortization of prior service cost	26	44	9
Recognized net actuarial loss	276	146	138
Net periodic pension expense	3,161	2,038	1,579
Accumulated benefit obligation and projected benefit obligation
Accumulated benefit obligation	9,867	8,208
Projected benefit obligation:
Beginning balance	11,928	10,524
Service cost	2,750	1,914
Interest cost	985	741	660
Actuarial (gain) loss	586	698
Benefits paid	(1,514)	(1,398)
Plan combination	97	259
Exchange rate adjustments	(1,003)	(810)
Ending balance	13,829	11,928	10,524
Fair value of plan assets
Beginning balance	10,055	9,885
Employer contributions	2,505	1,794
Actual return on plan assets	997	518
Actuarial loss		(3)
Benefits paid	(1,495)	(1,398)
Exchange rate adjustments	(705)	(741)
Ending balance	11,357	10,055	$ 9,885
Accrued employee compensation and benefits	79,373	74,801
India and Sri Lanka
Fair value of plan assets
Accrued employee compensation and benefits	$ 2,472	$ 1,873
Minimum
Actuarial assumptions
Discount rate (as a percent)	6.60%	7.10%	7.30%
Compensation increases (annual) (as a percent)	6.50%	5.00%	5.00%
Expected return on assets (as a percent)	7.00%	7.00%	7.50%
Maximum
Actuarial assumptions
Discount rate (as a percent)	9.25%	11.16%	10.34%
Compensation increases (annual) (as a percent)	7.00%	8.00%	8.00%
Expected return on assets (as a percent)	8.44%	11.87%	12.20%