Post-retirement Benefits - Pension liability (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Pension liability
PBO	$ 13,829	$ 11,928	$ 10,524
Fair value of plan assets	11,357	10,055	9,885
Funded status recognized	2,472	1,873
Amount recorded in accumulated other comprehensive income	2,298	2,402
Amount in accumulated other comprehensive income (loss) that is expected to be recognized as a component of net periodic benefit cost	418
Expected contribution to gratuity plans by employer	5,335
Pretax amounts of prior service cost recognized in accumulated other comprehensive income
Prior service cost	(26)	(44)	(9)
Net amortization gain (loss)	(276)	(146)	(138)
Total	(302)	$ (190)	$ (147)
Estimated future benefits payments
2021	2,047
2022	1,768
2023	1,939
2024	2,406
2025	2,913
2026- 2028	$ 15,399