Intangible Assets - Intangible Assets, Other than Capitalized Software Development Costs (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Mar. 31, 2020
Finite Lived Intangible Assets [Line Items]
Gross carrying amount	$ 153,150	$ 153,150
Accumulated amortization	(107,573)	(95,341)
Net intangible assets	45,577	57,809
Customer Relationships
Finite Lived Intangible Assets [Line Items]
Gross carrying amount	39,200	39,200
Accumulated amortization	(24,150)	(21,951)
Net intangible assets	15,050	17,249
Trade Names
Finite Lived Intangible Assets [Line Items]
Gross carrying amount	250	250
Accumulated amortization	(42)	(17)
Net intangible assets	208	233
Computer Software, Intangible Asset
Finite Lived Intangible Assets [Line Items]
Gross carrying amount	113,700	113,700
Accumulated amortization	(83,381)	(73,373)
Net intangible assets	$ 30,319	$ 40,327