Income Taxes - Tax Credit Carryforwards - Deferred Tax Assets (Details) - USD ($) $ in Millions	Mar. 31, 2019	Mar. 31, 2018
Domestic Tax Authority
Deferred Tax Assets, Tax Credit Carryforwards [Abstract]
Deferred tax assets related to research and development credits	$ 8.4	$ 9.0
State and Local Jurisdiction
Deferred Tax Assets, Tax Credit Carryforwards [Abstract]
Deferred tax assets related to research and development credits	$ 9.0	$ 10.2