Goodwill and Intangible Assets - Goodwill (Details) $ in Thousands	12 Months Ended
	Mar. 31, 2020 USD ($) item	Mar. 31, 2019 USD ($)
Goodwill:
Number of reportable segments | item	1
Changes in goodwill
Beginning balance	$ 279,543	$ 297,251
Goodwill arising from acquisitions	27,316
Purchase price adjustment		(7,407)
Foreign currency translation adjustments	(10,366)	(10,301)
Ending balance	296,493	$ 279,543
Acquisition costs and goodwill deductible for tax purposes	168,493
Acquisition costs and goodwill not deductible for tax purposes	140,903
Acquired certain assets of a small consulting company purchase price
Amount paid towards earn-out consideration	1,051
Fiscal 2020 aquisitions
Changes in goodwill
Ending balance	27,316
Acquired certain assets of a small consulting company purchase price
Cash paid at closing	9,651
Amount paid towards earn-out consideration	3,736
Probable and estimable value of the contingent consideration	3,994
Maximum | Fiscal 2020 aquisitions
Acquired certain assets of a small consulting company purchase price
Additional earn-out consideration	$ 9,853